1 | Bulbasaur | HeartGold | Prof. Oak2 | Ivysaur | HeartGold | Evolve Bulbasaur (Lv. 16) | 3 | Venusaur | HeartGold | Evolve Ivysaur (Lv. 32) | 4 | Charmander | HeartGold | Prof. Oak | 5 | Charmeleon | HeartGold | Evolve Charmander (Lv. 16) | 6 | Charizard | HeartGold | Evolve Charmeleon (Lv. 36) | 7 | Squirtle | HeartGold | Prof. Oak | 8 | Wartortle | HeartGold | Evolve Squirtle (Lv. 16) | 9 | Blastoise | HeartGold | Evolve Wartortle (Lv. 36) | 10 | Caterpie | HeartGold | Routes 2, 30, 31, Ilex Forest, National Park, Viridian Forest (Morning/Day)
| National Park (Bug-Catching Contest) Ilex Forest (Headbutt trees) 11 | Metapod | HeartGold | Routes 2, 30, 31, Ilex Forest, National Park, Viridian Forest (Morning/Day)
| National Park (Bug-Catching Contest) Route 47, Ilex Forest (Headbutt trees) 12 | Butterfree | HeartGold | Route 2 (Morning/Day)
| Viridian Forest (Morning) National Park (Bug-Catching Contest) Route 47, Ilex Forest (Headbutt trees) 13 | Weedle | HeartGold | National Park (Bug-Catching Contest) | 14 | Kakuna | HeartGold | National Park (Bug-Catching Contest) | 15 | Beedrill | HeartGold | National Park (Bug-Catching Contest) | 16 | Pidgey | HeartGold | Routes 1, 2, 5, 6, 25, 29, 30, 31, 35, 36, 37, National Park, Viridian Forest (Morning/Day) | 17 | Pidgeotto | HeartGold | Routes 2, 8, 13, 14, 15, 25, 37, 43, Viridian Forest | 18 | Pidgeot | HeartGold | Evolve Pidgeotto (Lv. 36) | 19 | Rattata | HeartGold | Routes 1, 3, 4, 7, 9, 11, 22, 29, 30, 31, 32, 33, 34, 38, 39, 46, Sprout Tower, Union Cave, Burned Tower, Bell Tower, Mt. Mortar, Tohjo Falls | 20 | Raticate | HeartGold | Routes 7, 9, 10, 26, 27, 38, 39, 47, Mt. Mortar, Union Cave, Burned Tower, Tohjo Falls, Safari Zone | 21 | Spearow | HeartGold | Routes 3, 4, 7, 9, 10, 22, 33, 42, 46, 47
| Safari Zone (Morning/Day) Routes 7, 11, 16, 33, 42, 44, 45, 46, Azalea Town, Vermilion City, Celadon City (Headbutt trees) Route 35 (Webster) 22 | Fearow | HeartGold | Routes 9, 10, 16, 17, 18, 22, 47, 48, Safari Zone | 23 | Ekans | HeartGold | Goldenrod Game Corner
| Safari Zone (Morning/Day) 24 | Arbok | HeartGold | Safari Zone (Morning/Day) | 25 | Pikachu | HeartGold | Viridian Forest
| Trade in Saffron City 26 | Raichu | HeartGold | Evolve Pikachu (Thunder Stone) | 27 | Sandshrew | HeartGold | Union Cave, Mt. Moon, Safari Zone | 28 | Sandslash | HeartGold | Routes 26, 27, Safari Zone, Mt. Moon | 29 | NidoranF | HeartGold | Routes 35, 36
Safari Zone (Morning/Day) | 30 | Nidorina | HeartGold | Routes 13, 14, 15
| Safari Zone (Night) 31 | Nidoqueen | HeartGold | Evolve Nidorina (Moon Stone) | 32 | NidoranM | HeartGold | Routes 35, 36
| Safari Zone (Morning/Day) 33 | Nidorino | HeartGold | Routes 13, 14, 15
Safari Zone (Night) | 34 | Nidoking | HeartGold | Evolve Nidorino (Moon Stone) | 35 | Clefairy | HeartGold | Mt. Moon
| Safari Zone (Night) 36 | Clefable | HeartGold | Evolve Clefairy (Moon Stone) | 37 | Vulipx | HeartGold | Trade | 38 | Ninetales | HeartGold | Trade | 39 | Jigglypuff | HeartGold | Routes 3, 4, Safari Zone | 40 | Wigglytuff | HeartGold | Evolve Jigglypuff (Moon Stone) | 41 | Zubat | HeartGold | Dark Cave, Union Cave, Slowpoke Well, Ilex Forest, Burned Tower, Mt. Mortar, Ice Path, Whirl Islands, Mt. Moon, Rock Tunnel, Seafoam Islands, Tohjo Falls
| Routes 3, 4, 32, 33, 42, Cliff Cave, Safari Zone (Night) 42 | Golbat | HeartGold | Cliff Cave, Dark Cave, Ice Path, Mt. Mortar, Mt. Silver Interior/Mountain side, Slowpoke Well, Union Cave, Cerulean Cave, Seafoam Islands, Tohjo Falls, Whirl Islands, Victory Road
| Safari Zone (Night) 43 | Oddish | HeartGold | Routes 5, 6, 24, 25, Ilex Forest, Safari Zone (Night) | 44 | Gloom | HeartGold | Routes 5, 47, 48 (Night) | 45 | Vileplume | HeartGold | Evolve Gloom (Leaf Stone) | 46 | Paras | HeartGold | National Park (Bug-Catching Contest)
| Ilex Forest, Mt. Moon, Safari Zone 47 | Parasect | HeartGold | Cerulean Cave, Safari Zone | 48 | Venonat | HeartGold | Routes 24, 25, 43
| National Park (Bug-Catching Contest) Route 43, Lake of Rage (Headbutt trees) 49 | Venomoth | HeartGold | Routes 24, 25 (Night) | 50 | Diglett | HeartGold | Route 48, Diglett's Cave, Safari Zone
| Vermillion City (Rock Smash) 51 | Dugtrio | HeartGold | Diglett's Cave | 52 | Meowth | HeartGold | Trade | 53 | Persian | HeartGold | Trade | 54 | Psyduck | HeartGold | Routes 6, 35, Ilex Forest, Seafoam Islands, Cerulean Cave, Safari Zone | 55 | Golduck | HeartGold | Routes 6, 35, Ilex Forest, Cerulean Cave (Surfing)
| Mt. Silver, Seafoam Islands 56 | Mankey | HeartGold | Routes 9, 42 | 57 | Primeape | HeartGold | Route 9, Cerulean Cave | 58 | Growlithe | HeartGold | Routes 7, 8, 36, 37, 48 | 59 | Arcanine | HeartGold | Evolve Growlithe (Fire Stone) | 60 | Poliwag | HeartGold | Routes 22, 28, 30, 31, 44, Violet City, Ecruteak City, Viridian City, Mt. Silver Exterior (Surfing and fishing)
| Routes 6, 35, 43, 45, Ruins of Alph, Ilex Forest, Blackthorn City (Fishing) Cliff Edge Gate (Good Rod and Super Rod) Cerulean Cave (Old Rod and Good Rod) Safari Zone, Mt. Moon Square (Surfing and fishing) 61 | Poliwhirl | HeartGold | Routes 22, 28, 30, 31, 44, Ecruteak City, Mt. Silver, Violet City, Viridian City, Mt. Silver (Surfing)
| Cerulean Cave (Super Rod) (Morning/Day) Safari Zone (Fishing or surfing) 62 | Poliwrath | HeartGold | Evolve Poliwhirl (Water Stone) | 63 | Abra | HeartGold | Routes 5, 6, 8, 24, 25, 34, 35, Safari Zone, Goldenrod Game Corner | 64 | Kadabra | HeartGold | Route 8, Cerulean Cave | 65 | Alakazam | HeartGold | Evolve Kadabra (Trade) | 66 | Machop | HeartGold | Cliff Cave, Rock Tunnel, Mt. Mortar
| Safari Zone (Morning/Day) Trade Drowzee in Goldenrod Department Store 67 | Machoke | HeartGold | Cliff Cave, Mt. Mortar, Cerulean Cave, Rock Tunnel, Safari Zone | 68 | Machamp | HeartGold | Evolve Machoke (Trade) | 69 | Bellsprout | HeartGold | Routes 5, 6, 24, 25, 31, 32, 44 | 70 | Weepinbell | HeartGold | Routes 24, 25, 44, Safari Zone | 71 | Victreebel | HeartGold | Evolve Weepinbell (Leaf Stone) | 72 | Tentacool | HeartGold | Routes 20, 21, 26, 27, 41, 47, New Bark Town, Vermilion City, Cinnabar Island, Pallet Town (Surfing, Old/Good Rod)
| Routes 19, 34, 40, Cherrygrove City, Olivine City, Cianwood City, Union Cave, Whirl Islands (Surfing) Routes 13, 32 (Surfing or fishing) Route 12 (Fishing) 73 | Tentacruel | HeartGold | Routes 20, 21, 26, 27, 41, New Bark Town, Vermilion City, Cinnabar Island, Pallet Town (Surfing and Super Rod)
| Routes 12, 13, 19, 32, 34, 40, Cherrygrove City, Union Cave, Whirl Islands, Olivine City, Cianwood City (Surfing) Route 47 (Super Rod) 74 | Geodude | HeartGold | Routes 45, 46, Union Cave, Dark Cave, Ruins of Alph, Mt. Mortar, Cliff Cave, Victory Road, Rock Tunnel, Mt. Moon, Safari Zone, Cerulean Cave
| Team Rocket HQ 75 | Graveler | HeartGold | Route 45, Cliff Cave, Victory Road, Dark Cave, Mt. Mortar, Mt. Silver, Cerulean Cave
| Safari Zone (Morning/Day) 76 | Golem | HeartGold | Evolve Graveler (Trade) | 77 | Ponyta | HeartGold | Routes 22, 26, 27, 28, Mt. Silver, Safari Zone | 78 | Rapidash | HeartGold | Route 28, Mt. Silver | 79 | Slowpoke | HeartGold | Slowpoke Well, Tohjo Falls (Surfing) | 80 | Slowbro | HeartGold | Slowpoke Well, Safari Zone, Seafoam Islands | 81 | Magnemite | HeartGold | Routes 6, 11, 38, 39, Safari Zone | 82 | Magneton | HeartGold | Cerulean Cave, Safari Zone
| Trade Dugtrio in Power Plant 83 | Farfetch'd | HeartGold | Routes 38, 39, 47, 48, Safari Zone | 84 | |