You cannot catch any of the Pokémon that are not in the Sinnoh Pokédex until you acquire the National Pokédex. You must see all 150 Sinnoh Pokémon. Once you do so, you must visit Prof. Rowan in Sandgem Town. When you talk to him, Prof. Oak will rush in and upgrade your Pokédex to the National Dex. Once he does so, you can import any Pokémon from FireRed, LeafGreen, Ruby, Sapphire, and Emerald, by putting that game in the DS's GBA slot and selecting the Transfer option at the Diamond/Pearl Main Menu. Once you transfer Pokémon from the GBA games, they will be gone forever from the GBA games. After you transfer Pokémon to Diamond/Pearl, you must then capture them in the Pal Park (directly south of Sandgem Town; go to Sandgem Beach and Surf to the area near the Pal Park).
To see Dialga, (in Diamond) or Palkia, (in Pearl), you must speak with the Elder of Celestic Town (the old lady in the big house.) She will then show you a picture of Dialga/Palkia, adding the 150th Pokémon to the Sinnoh Pokédex.
Migration Pokémon[edit]
Some Pokémon cannot be obtained in Sinnoh. These Pokémon must be migrated from either Pokémon FireRed, Pokémon LeafGreen, Pokémon Ruby, Pokémon Sapphire, or Pokémon Emerald via Pal Park. These Pokémon are listed below.
Underground Pokémon[edit]
Check out The Underground to see how to obtain the following Pokémon.
| Pokémon | Fossil |
|---|---|
 Cranidos
|
Skull Fossil |
 Shieldon
|
Armor Fossil |
 Kabuto
|
Dome Fossil |
 Omanyte
|
Helix Fossil |
 Anorith
|
Claw Fossil |
 Lileep
|
Root Fossil |
 Aerodactyl
|
Old Amber |
Version exclusives[edit]
Dual-slot Pokémon[edit]
Dual-slot mode, is a way that you can obtain more Pokémon that are in the National Pokédex, by putting in a Ruby, Sapphire, Emerald, FireRed or LeafGreen cartridge into the DS slot.
The below table shows which game needs to be inserted to get the Pokémon. Check out Dual-slot mode for the locations of the Pokémon.
NPC and side quests[edit]
| Pokémon | How to obtain |
|---|---|
 Cresselia
|
Fullmoon Island |
 Giratina
|
Turnback Cave |
 Regigigas
|
Snowpoint City Temple |
 Spiritomb
|
Hallowed Tower |
 Eevee
|
Bebe |
Evolution[edit]
Some Pokémon require special steps to evolve their base forms.
Evolutionary Stones[edit]
There are 16 Pokémon that can be obtained when you use a Stone on their unevolved forms.
Trading[edit]
The following Pokémon need to be traded to evolve.
| Evolution | Requirements |
|---|---|
 Alakazam |
Trade Kadabra |
 Machamp |
Trade Machoke |
 Golem |
Trade Graveler |
 Gengar |
Trade Haunter |
 Slowking |
Trade Slowpoke holding King's Rock |
 Politoed |
Trade Poliwhirl holding King's Rock |
 Steelix |
Trade Onix holding Metal Coat |
 Scizor |
Trade Scyther holding Metal Coat |
 Kingdra |
Trade Seadra holding Dragon Scale |
 Porygon2 |
Trade Porygon holding Up-Grade |
 Huntail |
Trade Clamperl holding Deep Sea Tooth |
 Gorebyss |
Trade Clamperl holding Deep Sea Scale |
 Rhyperior |
Trade Rhydon holding Protector |
 Electivire |
Trade Electabuzz holding Electirizer |
 Huntail |
Trade Magmar holding Magmarizer |
 Porygon-Z |
Trade Porygon2 holding Dubious Disc |
 Dusknoir |
Trade Dusclops holding Reaper Cloth |
Friendship[edit]
The following Pokémon need at least 220 friendship to evolve.
| Evolution | Requirements |
|---|---|
 Blissey |
Chansey |
 Crobat |
Golbat |
 Togetic |
Togepi |
 Pikachu |
Pichu |
 Clefairy |
Cleffa |
| Togetic |
Togepi |
 Jigglypuff |
Igglybuff |
 Espeon |
Eevee during day |
 Umbreon |
Eevee during night |
 Marill |
Azurill |
 Roselia |
Budew during morning or day |
 Lopunny |
Buneary |
 Chimecho |
Chingling during night |
 Snorlax |
Munchlax |
 Lucario |
Riolu during day |
Manaphy & Phione[edit]
You can only obtain Manaphy through Pokémon Ranger and you can only get Phione through breeding Manaphy.
Check out Obtaining Manaphy
Nintendo Events[edit]
These Pokémon were obtainable through events which have passed which means you can only get them through trading or cheating.
| Pokémon | How to obtain |
|---|---|
 Darkrai
|
Newmoon Island |
 Shaymin
|
Flower Paradise |
 Arceus
|
Hall of Origin |