How Many Pokémon Can You Get with Only Pokémon Brilliant Diamond?
Assuming you do not use any glitches, the answer is 433. Three Mythical Pokémon (Mew, Jirachi, and Arceus) can also be obtained if the player has access to Let's Go Pikachu/Eevee, Sword/Shield, and Legends: Arceus save data, respectively, which puts the total with extra save data at 436. The Professor Oak challenge guide for Brilliant Diamond can be found here, although I've made a shorter list of encounters below in case anything happens to the external guide.
The list of Pokémon you cannot get without trading, which equals 433 species, is as follows:
- Trade Evolutions (16) - 16 total
- Alakazam, Golem, Machamp, Gengar, Politoed, Slowking, Rhyperior, Kingdra, Scizor, Electivire, Magmortar, Porygon2, Porygon-Z, Dusknoir, Huntail, and Gorebyss evolve by trade. Without the ability to trade, they are unobtainable.
- Version Exclusives (35) - 51 total
- The following Pokémon cannot be obtained without the use of glitches or trading: Shieldon, Bastiodon, Misdreavus, Mismagius, Glameow, Purugly, Palkia, Weedle, Kakuna, Beedrill, Sandshrew, Sandslash, Vulpix, Ninetales, Slowpoke, Slowbro, Magby, Magmar,
Pinsir, Articuno, Zapdos, Moltres, Teddiursa, Ursaring, Stantler, Lugia, Lotad, Lombre, Ludicolo, Sableye, Seviper, Lunatone, Bagon, Shelgon, and Salamence.
- Mythical/Event (9) - 60 total
- Celebi, Deoxys, Phione, Manaphy, Darkrai, and Shaymin are only obtainable via events that are no longer active, may be difficult to come by in the future, or require communication with additional software. Extra save data provides access to Mew, Jirachi, and Arceus, but this setup may not work on future hardware systems or releases.
Professor Oak Challenge Notes
Pre-Badge 1 (Roark) - 29 Total Pokémon
- Gift at Lake Verity: One starter & its evolutions (3 total)
- Walking on Route 201: Bidoof, Bibarel (5 total)
- Walking on Route 201: Starly, Staravia, Staraptor (8 total)
- Walking on Route 202: Shinx, Luxio, Luxray (11 total)
- Walking on Route 202: Kricketot, Kricketune (13 total)
- Fishing (Old Rod) on Route 218: Magikarp, Gyarados (15 total)
- Walking on Route 204 (southern half): Budew, Roselia (17 total)
- Walking in Ravaged Path: Psyduck, Golduck (19 total)
- Walking in Ravaged Path: Geodude, Graveler (21 total)
- Walking in Ravaged Path: Zubat, Golbat, Crobat (24 total)
- Walking on Route 203: Abra, Kadabra (26 total)
- Walking in Oreburgh Mine: Onix (27 total)
- Walking on Route 207: Machop, Machoke (29 total)
Badge 1 through Badge 2 (Gardenia) - 107 Total Pokémon
If you are able to obtain Mew and Jirachi, the total for this section is 109.
- Gift in Floaroma Town (with Let's Go Pikachu/Eevee data): Mew
- Gift in Floaroma Town (with Sword/Shield data): Jirachi
- Walking at the Valley Windworks: Shellos, Gastrodon (31 total)
- Walking at the Valley Windworks: Buizel, Floatzel (33 total)
- Walking at the Valley Windworks: Pachirisu (34 total)
- Static encounter at the Valley Windworks: Drifloon, Drifblim (36 total)
- Honey Tree (Floaroma Meadow, Valley Windworks, two on Route 205): Wurmple, Silcoon, Beautifly, Cascoon, Dustox (41 total)
- Honey Tree (Floaroma Meadow, Valley Windworks, two on Route 205): Aipom, Ambipom (43 total)
- Honey Tree (Floaroma Meadow, Valley Windworks, two on Route 205): Burmy, Wormadam, Mothim (46 total)
- Honey Tree (Floaroma Meadow, Valley Windworks, two on Route 205): Cherubi, Cherrim (48 total)
- Honey Tree (Floaroma Meadow, Valley Windworks, two on Route 205): Combee, Vespiquen (50 total)
- Honey Tree (Floaroma Meadow, Valley Windworks, two on Route 205): Heracross (51 total)
- Honey Tree (Floaroma Meadow, Valley Windworks, two on Route 205): Munchlax, Snorlax (53 total) - note that a Munchlax tree may not be available as one of the four trees you can encounter before fighting Gardenia; either ensure your Trainer ID allows you an early Munchlax tree (check it here) or wait until later.
- Walking in Eterna Forest: Buneary, Lopunny (55 total)
- Walking in Eterna Forest: Murkrow (56 total)
- In-game Trade in Eterna City: Chatot: Trade your Buizel (57 total)
- Revive the Skull Fossil (obtained through the Grand Underground) in Oreburgh Museum: Cranidos, Rampardos (59 total)
- Walking in the Grand Underground: Gastly, Haunter (61 total)
- Walking in the Grand Underground: Skorupi, Drapion (63 total)
- Walking in the Grand Underground: Croagunk, Toxicroak (65 total)
- Walking in the Grand Underground: Magnemite, Magneton, Magnezone (68 total)
- Walking in the Grand Underground: Lickitung, Lickilicky (70 total)
- Walking in the Grand Underground: Rhyhorn, Rhydon (72 total)
- Walking in the Grand Underground: Houndoom (73 total)
- Walking in the Grand Underground: Swablu, Altaria (75 total)
- Walking in the Grand Underground: Absol (76 total)
- Walking in the Grand Underground: Scyther (77 total)
- Walking in the Grand Underground: Togepi, Togetic (79 total)
- Walking in the Grand Underground: Ralts, Kirlia, Gardevoir (82 total)
- Walking in the Grand Underground: Gligar (83 total)
- Walking in the Grand Underground: Swinub, Piloswine, Mamoswine (86 total; need to find a Swinub with Ancient Power as its egg move, or wait until Pastoria to re-learn it)
- Walking in the Grand Underground: Smoochum, Jynx (88 total)
- Walking in the Grand Underground: Elekid, Electabuzz (90 total)
- Walking in the Grand Underground: Duskull, Dusclops (92 total)
- Walking on Route 211 (western half): Meditite, Medicham (94 total)
- Walking on Route 211 (western half): Chingling, Chimecho (96 total)
- Walking on Route 211 (western half): Ponyta, Rapidash (98 total)
- Walking on Route 211 (western half): Hoothoot, Noctowl (100 total)
- Walking in Mt. Coronet 1F north (toward Route 211): Cleffa, Clefairy (102 total)
- Get a Moon Stone via mining in the Grand Underground: Evolve Clefairy (103 total)
- Get a Shiny Stone via Pickup (level 11+ Pickup user): Evolve Roselia (104 total)
- Get a Dusk Stone via Pickup (level 11+ Pickup user): Evolve Murkrow (105 total)
- Get a Dawn Stone via Pickup (level 11+ Pickup user): Evolve Kirlia (106 total)
- Get a Shiny Stone via Pickup (level 11+ Pickup user): Evolve Togetic (107 total)
Badge 2 through Badge 3 (Maylene) - 141 Total Pokémon
If you are able to obtain Mew and Jirachi, the total for this section is 143.
- Walking on Route 206: Stunky, Skuntank (109 total)
- Walking on Route 206: Bronzor, Bronzong (111 total)
- Gift (Egg) in Hearthome City: Happiny, Chansey, Blissey (114 total)
- Walking on Route 209: Mime Jr., Mr. Mime (116 total)
- Fishing (Good Rod) on Route 209: Goldeen, Seaking (118 total)
- Static encounter at the Hallowed Tower: Spiritomb (119 total)
- Fishing (Good Rod) in Mt. Coronet: Barboach, Whiscash (121 total)
- Fishing (Good Rod) on Route 205 (southern half): Finneon, Lumineon (123 total)
- Solaceon Town: Breed Houndoom to get Houndour (124 total)
- Walking in the Solaceon Ruins: Unown (125 total)
- Walking on Route 214: Girafarig (126 total)
- Walking in the Maniac Tunnel: Hippopotas, Hippowdon (128 total)
- Walking on Route 213: Wingull, Pelipper (130 total)
- Fishing (Good Rod) on Route 213: Remoraid, Octillery (132 total)
- Walking in the Great Marsh: Wooper, Quagsire (134 total)
- Walking in the Great Marsh: Azurill, Marill, Azumarill (137 total)
- Walking (special encounter) in the Great Marsh: Carnivine (138 total)
- Walking in the Trophy Garden: Pichu, Pikachu (140 total)
- Get a Thunder Stone via mining in the Grand Underground: Evolve Pikachu (141 total)
Badges 3 through 5 (Fantina) - 144 Total Pokémon
If you are able to obtain Mew and Jirachi, the total for this section is 146.
Badge 5 through 6 (Byron) - 149 Total Pokémon
If you are able to obtain Mew and Jirachi, the total for this section is 151.
- Surfing on Route 218: Tentacool, Tentacruel (146 total)
- Walking in Iron Island B2F west and B3F: Steelix (147 total)
- Gift (Egg) in Iron Island B2F west: Riolu, Lucario (149 total)
Badge 6 through 7 (Candice) - 157 Total Pokémon
If you are able to obtain Mew and Jirachi, the total for this section is 159.
- Walking in Wayward Cave B1F: Gible, Gabite, Garchomp (152 total)
- Fishing (any Rod) in Mt. Coronet B1F: Feebas, Milotic (154 total)
- Walking on Route 216: Snover, Abomasnow (156 total)
- Walking on Route 216: Sneasel (157 total)
Badge 7 through 8 (Volkner) - 172 Total Pokémon
If you are able to obtain Mew and Jirachi, the total for this section is 174.
- Static encounter at Spear Pillar: Dialga (158 total)
- Surfing in Sunyshore City: Mantyke, Mantine (160 total)
- Revive the Dome Fossil (obtained through the Underground) in Oreburgh Museum: Kabuto, Kabutops (162 total)
- Revive the Helix Fossil (obtained through the Underground) in Oreburgh Museum: Omanye, Omastar (164 total)
- Revive the Old Amber (obtained through the Underground) in Oreburgh Museum: Aerodactyl (165 total)
- Revive the Root Fossil (obtained through the Underground) in Oreburgh Museum: Lileep, Cradily (167 total)
- Revive the Claw Fossil (obtained through the Underground) in Oreburgh Museum: Anorith, Armaldo (169 total)
- Static encounter at Lake Acuity: Uxie (170 total)
- Static encounter at Lake Valor: Azelf (171 total)
- Roaming Legend: Mesprit (172 total)
Badge 8 through Elite Four - 388 Total Pokémon
If you are able to obtain Mew and Jirachi, the total for this section is 390.
If the player battles every Trainer in the region and makes sure to catch all Pokémon as outlined above, they will actually be able to obtain the National Pokédex before defeating the Elite Four. (Players that chose Piplup will need to lose to Flint after seeing his Infernape.) Many encounters are tied to obtaining the National Pokédex, and those encounters will all be listed in this section.
- Evolve Sneasel by leveling up with a Razor Claw from Victory Road: Weavile (173 total)
- Walking in the Trophy Garden: Igglybuff, Jigglypuff, Wigglytuff (176 total)
- Walking in the Trophy Garden: Meowth, Persian (178 total)
- Walking in the Trophy Garden: Eevee, Vaporeon, Jolteon, Flareon, Espeon, Umbreon, Leafeon, Glaceon (186 total)
- Walking in the Trophy Garden: Porygon (187 total)
- Walking in the Trophy Garden: Plusle (188 total)
- Walking in the Trophy Garden: Minun (189 total)
- Walking in the Trophy Garden: Castform (190 total)
- Walking in the Trophy Garden: Bonsly, Sudowoodo (192 total)
- Walking on Route 212 (northern half) (Poké Radar): Smeargle (193 total)
- Walking on Route 213 (Poké Radar): Swellow (194 total)
- Walking on Mt. Coronet mountainside (Poké Radar): Loudred, Exploud (196 total)
- Walking (special encounter) in the Great Marsh: Exeggcute, Exeggutor (198 total)
- Walking (special encounter) in the Great Marsh: Kangaskhan (199 total)
- Walking (special encounter) in the Great Marsh: Yanma, Yanmega (201 total)
- Walking (special encounter) in the Great Marsh: Shroomish, Breloom (203 total)
- Walking (special encounter) in the Great Marsh: Gulpin, Swalot (205 total)
- Static encounter in Old Chateau (in the haunted TV on 2F): Rotom (206 total)
- Walking in the Grand Underground: Bulbasaur, Ivysaur, Venusaur (209 total)
- Walking in the Grand Underground: Charmander, Charmeleon, Charizard (212 total)
- Walking in the Grand Underground: Squirtle, Wartortle, Blastoise (215 total)
- Walking in the Grand Underground: Caterpie, Metapod, Butterfree (218 total)
- Walking in the Grand Underground: Rattata, Raticate (220 total)
- Walking in the Grand Underground: Ekans, Arbok (222 total)
- Walking in the Grand Underground: Nidoran♀, Nidorina, Nidoqueen (225 total)
- Walking in the Grand Underground: Nidoran♂, Nidorino, Nidoking (228 total)
- Walking in the Grand Underground: Oddish, Gloom, Vileplume, Bellossom (232 total)
- Walking in the Grand Underground: Paras, Parasect (234 total)
- Walking in the Grand Underground: Venonat, Venomoth (236 total)
- Walking in the Grand Underground: Mankey, Primeape (238 total)
- Walking in the Grand Underground: Growlithe, Arcanine (240 total)
- Walking in the Grand Underground: Poliwag, Poliwhirl, Poliwrath (243 total)
- Walking in the Grand Underground: Bellsprout, Weepinbell, Victreebel (246 total)
- Walking in the Grand Underground: Farfetch'd (247 total)
- Walking in the Grand Underground: Doduo, Dodrio (249 total)
- Walking in the Grand Underground: Seel, Dewgong (251 total)
- Walking in the Grand Underground: Grimer, Muk (253 total)
- Walking in the Grand Underground: Shellder, Cloyster (255 total)
- Walking in the Grand Underground: Drowzee, Hypno (257 total)
- Walking in the Grand Underground: Krabby, Kingler (259 total)
- Walking in the Grand Underground: Voltorb, Electrode (261 total)
- Walking in the Grand Underground: Cubone, Marowak (263 total)
- Walking in the Grand Underground: Tyrogue, Hitmonlee, Hitmonchan, Hitmontop (267 total)
- Walking in the Grand Underground: Weezing (268 total)
- Walking in the Grand Underground: Tangela, Tangrowth (270 total)
- Walking in the Grand Underground: Horsea, Seadra (272 total)
- Walking in the Grand Underground: Staryu, Starmie (274 total)
- Walking in the Grand Underground: Tauros (275 total)
- Walking in the Grand Underground: Ditto (276 total)
- Walking in the Grand Underground: Dratini, Dragonair, Dragonite (279 total)
- Walking in the Grand Underground: Chikorita, Bayleef, Meganium (282 total)
- Walking in the Grand Underground: Cyndaquil, Quilava, Typhlosion (285 total)
- Walking in the Grand Underground: Totodile, Croconaw, Feraligatr (288 total)
- Walking in the Grand Underground: Sentret, Furret (290 total)
- Walking in the Grand Underground: Ledian (291 total)
- Walking in the Grand Underground: Ariados (292 total)
- Walking in the Grand Underground: Chinchou, Lanturn (294 total)
- Walking in the Grand Underground: Natu, Xatu (296 total)
- Walking in the Grand Underground: Mareep, Flaaffy, Ampharos (299 total)
- Walking in the Grand Underground: Hoppip, Skiploom, Jumpluff (302 total)
- Walking in the Grand Underground: Sunkern, Sunflora (304 total)
- Walking in the Grand Underground: Wobbuffet (305 total)
- Walking in the Grand Underground: Pineco, Forretress (307 total)
- Walking in the Grand Underground: Snubbull, Granbull (309 total)
- Walking in the Grand Underground: Qwilfish (310 total)
- Walking in the Grand Underground: Shuckle (311 total)
- Walking in the Grand Underground: Slugma, Magcargo (313 total)
- Walking in the Grand Underground: Corsola (314 total)
- Walking in the Grand Underground: Delibird (315 total)
- Walking in the Grand Underground: Phanpy, Donphan (317 total)
- Walking in the Grand Underground: Miltank (318 total)
- Walking in the Grand Underground: Larvitar, Pupitar, Tyranitar (321 total)
- Walking in the Grand Underground: Treecko, Grovyle, Sceptile (324 total)
- Walking in the Grand Underground: Torchic, Combusken, Blaziken (327 total)
- Walking in the Grand Underground: Mudkip, Marshtomp, Swampert (330 total)
- Walking in the Grand Underground: Poochyena, Mightyena (332 total)
- Walking in the Grand Underground: Zigzagoon, Linoone (334 total)
- Walking in the Grand Underground: Seedot, Nuzleaf, Shiftry (337 total)
- Walking in the Grand Underground: Surskit, Masquerain (339 total)
- Walking in the Grand Underground: Nincada, Ninjask, Shedinja (342 total)
- Walking in the Grand Underground: Skitty, Delcatty (344 total)
- Walking in the Grand Underground: Mawile (345 total)
- Walking in the Grand Underground: Aron, Lairon, Aggron (348 total)
- Walking in the Grand Underground: Volbeat (349 total)
- Walking in the Grand Underground: Illumise (350 total)
- Walking in the Grand Underground: Carvanha, Sharpedo (352 total)
- Walking in the Grand Underground: Numel, Camerupt (354 total)
- Walking in the Grand Underground: Torkoal (355 total)
- Walking in the Grand Underground: Trapinch, Vibrava, Flygon (358 total)
- Walking in the Grand Underground: Cacnea, Cacturne (360 total)
- Walking in the Grand Underground: Zangoose (361 total)
- Walking in the Grand Underground: Solrock (362 total)
- Walking in the Grand Underground: Corphish, Crawdaunt (364 total)
- Walking in the Grand Underground: Baltoy, Claydol (366 total)
- Walking in the Grand Underground: Kecleon (367 total)
- Walking in the Grand Underground: Banette (368 total)
- Walking in the Grand Underground: Tropius (369 total)
- Walking in the Grand Underground: Walrein (370 total)
- Walking in the Grand Underground: Clamperl (371 total)
- Walking in the Grand Underground: Beldum, Metang, Metagross (374 total)
- Walking in the Grand Underground: The other two Sinnoh starters and their evolutions (380 total)
- Solaceon Town: Breed Swellow to get Taillow (381 total)
- Solaceon Town: Breed Loudred or Exploud to get Whismur (382 total)
- Solaceon Town: Breed Weezing to get Koffing (383 total)
- Solaceon Town: Breed Ledian to get Ledyba (384 total)
- Solaceon Town: Breed Ariados to get Spinarak (385 total)
- Solaceon Town: Breed Banette to get Shuppet (386 total)
- Solaceon Town: Breed Walrein to get Spheal and evolve into Sealeo (388 total)
Post-Elite Four - National Pokédex - 433 Total Pokémon
If you are able to obtain Mew, Jirachi, and Arceus, the total for this section is 436.
The Super Rod is at the Fight Area.
- Walking at the Valley Windworks (Swarm): Electrike, Manectric (390 total)
- Walking in Eterna Forest (Swarm): Slakoth, Vigoroth, Slaking (393 total)
- Walking on Route 206 (Swarm): Nosepass, Probopass (395 total)
- Walking on Route 208 (Swarm): Dunsparce (396 total)
- Walking on Route 214 (Swarm): Spoink, Grumpig (398 total)
- Static encounter in Turnback Cave: Giratina (399 total)
- Fishing (Super Rod) on Route 223: Wailmer, Wailord (401 total)
- Fishing (Super Rod) in Pokémon League: Luvdisc (402 total)
- Surfing in Victory Road 1F back 2: Lapras (403 total)
- Walking on Route 225: Spearow, Fearow (405 total)
- Walking on Route 225 (Swarm): Makuhita, Hariyama (407 total)
- Fishing (Super Rod) on Route 226: Relicanth (408 total)
- Walking on Route 227: Skarmory (409 total)
- Walking on Route 227 (Swarm): Spinda (410 total)
- Static encounter in Stark Mountain: Heatran (411 total)
- Walking on Route 228: Diglett, Dugtrio (413 total)
- Walking on Route 229 (Swarm): Pidgey, Pidgeotto, Pidgeot (416 total)
- Solaceon Town: Breed Wobbuffet to get Wynaut (417 total)
- Evolve Gligar by leveling up with a Razor Fang from the Battle Park: Gliscor (418 total)
- Roaming Legend: Cresselia (419 total)
- Static encounter at Ramanas Park: Regirock, Regice, Registeel (422 total)
- Static encounter at Ramanas Park: Raikou, Entei, Suicune (425 total)
- Static encounter at Ramanas Park: Latias, Latios (427 total)
- Static encounter at Ramanas Park: Ho-Oh (428 total)
- Static encounter at Ramanas Park: Kyogre, Groudon, Rayquaza (431 total)
- Static encounter at Ramanas Park: Mewtwo (432 total)
- Static encounter at Snowpoint Temple: Regigigas (433 total)
- Static encounter in the Hall of Origin (with Legends: Arceus data & all Missions completed): Arceus