Slowbro losing Shellder

Devolution (Japanese: 退化 degeneration) is the process of an evolved Pokémon reverting to its previous form. This is not nearly as well-known among the fandom as evolution is, due to devolution being impossible within the games and anime. In most media in which it exists, devolution is not nearly as commonplace as evolution, and is generally brought about mainly through artificial means, such as sprays or genetic engineering.

In the core series games

Slowking losing Shellder

While devolution is not possible within the core series games, the notion is referred to by Slowbro's numerous Pokédex entries. Said entries claim that if the Shellder falls off, the Slowbro turns back into a Slowpoke. It is said that if Slowking loses its Shellder, it forgets everything it has learned.[1]

A similar situation applies to Exeggutor, as it is stated in its Pokédex entries that if one of its heads were to fall off, that head would become an Exeggcute.

In the spin-off games

Pokémon Mystery Dungeon

The only Pokémon games in which devolution is possible are games from the Pokémon Mystery Dungeon series games of the Nintendo 3DS.

In Pokémon Mystery Dungeon: Gates to Infinity, the Devolve Orb is a Wonder Orb that devolves all enemies in the room.

Spoiler warning: this article may contain major plot or ending details.

In Pokémon Super Mystery Dungeon, the player and their partner evolve and later devolve three times during the game's main story, thanks to the Harmony Scarves they wear.

  Spoilers end here.  

Pokémon Trading Card Game

Pokémon cards can devolve in Pokémon Trading Card Game video games, which contain cards that can cause devolution.

Pokémon UNITE

The opening cutscene for Pokémon UNITE shows Talonflame, Slowbro, Greninja, Cinderace, and Garchomp devolving into their base forms of Fletchling, Slowpoke, Froakie, Scorbunny, and Gible, respectively. This suggests that experienced Pokémon that participate in Unite Battles are devolved to their base forms inside the stadium in order to evolve again during the game. However, Pokémon with baby forms, such as Pikachu and Mr. Mime, do not devolve to their baby stages.

In the anime

Wobbuffet devolving in the anime

In the Pokémon anime, the subject of devolution has rarely been brought up. Misty explicitly states in Electric Shock Showdown that evolution cannot be reversed, effectively confirming the nonexistence of devolution within the anime. This was reconfirmed in A Stealthy Challenge!, where Bonnie asked Frogadier to devolve into Froakie so she could see it evolve again, but Clemont explained that it doesn't work that way.

In Dream a Little Dream from Me!, Ash's Pikachu had a nightmare featuring Frogadier having devolved into Froakie. Clemont's Bunnelby, which appeared as a Diggersby in the same nightmare, also devolved back into its first stage later in the dream.

The first known instance of a real devolution in the anime occurred when Faba fitted Silvally with a restraining mask, thereby turning it into a Type: Null.

In The Gates of Warp!, Pokémon in an alternate world version of Sinnoh devolved due to Dialga and Palkia's battle, with most of them eventually reverting all the way into Eggs. In Showdown at the Gates of Warp!, this battle was revealed to have been orchestrated by Alternate World Team Rocket to make Pokémon easier to steal and train to serve them. Once they had been defeated, Ash, Dawn, Goh, Chloe, and their alternate world counterparts prayed for Arceus to stop the fight, which it did. Afterwards, Dialga and Palkia restored the reverted Pokémon to normal, fulfilling everyone's wish.

In the manga

Eevee devolving from Jolteon in Pokémon Adventures

Pokémon Adventures

Before Vee, Red's Eevee, evolved into Espeon, he had been the subject of an experiment by Team Rocket, which allowed him to evolve into any of his three evolutions that were known at the time. He was also able to devolve back into an Eevee and evolve into a different Eeveelution. Although this does mean that devolution is possible in Pokémon Adventures, the artificial means through which this was achieved and the lack of any other instances of devolution suggest that it may not be possible through natural means.

Pokémon Horizon

Akira's Rockruff has the unique ability to evolve into Lycanroc and then devolve into Rockruff again, thanks to the strange red stone on its neck. It also has the ability to change in between its Midday and Midnight Forms while being evolved.

Pokémon Pocket Monsters

Unlike any other media, Pokémon are capable of devolving just as easily as they evolve in Pokémon Pocket Monsters. This became especially evident when Red's Clefairy and Pikachu evolve into Clefable and Raichu respectively, then revert to their original forms, as well as when Green's Charmander evolved into Charizard and then turned back into Charmander.

In the TCG

Devolution Spray, one of the few methods of inducing devolution in the TCG

In the TCG, devolution is perfectly possible, albeit not at a player's whim. Devolution must be induced by the effects of an attack, a Poké-Power, or a Trainer card. Examples include Mew's Devolution Beam attack, Flareon's Undevelop Poké-Power, and the Devolution Spray Item. The following is a list of cards that can achieve devolution.

Related cards
Cards listed with a blue background are only legal to use in the current Expanded format.
Cards listed with a silver background are legal to use in both the current Standard and Expanded formats.
Card Type English
Rarity # Japanese
Rarity #
Devolution Spray I Base Set   72/102 Expansion Pack    
Dragons Exalted   113/124 Dragon Blast   048/050
      BW-P Promotional cards   196/BW-P
Fates Collide   95/124 Awakening Psychic King   067/078
Evolutions   76/108 Expansion Pack 20th Anniversary   075/087
Mew   Wizards Black Star Promos   8      
Wizards Black Star Promos   9 Mystery of the Fossils    
Hyper Devolution Spray T Neo Discovery   73/75 Crossing the Ruins...    
      Pokémon Web   031/048
Mew ex         PLAY Promotional cards   007/PLAY
Omastar   EX Sandstorm   19/100 Magma VS Aqua: Two Ambitions   024/080
EX Power Keepers   20/108 World Champions Pack   017/108
Mew ex   EX Holon Phantoms   100/110 Mew Quarter Deck   003/015
Flareon   Rising Rivals   19/111 Bonds to the End of Time   011/090
Jolteon   Rising Rivals   26/111 Bonds to the End of Time   028/090
Vaporeon   Rising Rivals   34/111 Bonds to the End of Time   014/090
Jirachi   Unleashed   1/95 Metagross Deck   006/014
Call of Legends   11/95      
Golurk   Dragons Exalted   59/124 Dragon Blade   023/050
Boundaries Crossed   150/149 Freeze Bolt   064/059
Claydol   Ancient Origins   33/98 Bandit Ring   033/081
Porygon-Z   Ancient Origins   67/98 Bandit Ring   067/081
Espeon    BREAKpoint   52/122 Rage of the Broken Heavens   035/080
BREAKpoint   117/122 Rage of the Broken Heavens   084/080
      The Best of XY   045/171
Porygon-Z   Burning Shadows   105/147 Darkness that Consumes Light   044/051
Miscellaneous Promotional cards   105a/147 SM-P Promotional cards   070/SM-P
Shining Jirachi   Shining Legends   42/73 Shining Legends   043/072
Celebi     Lost Thunder   19/214 Super-Burst Impact   015/095
Dialga   Lost Thunder   127/214 Thunderclap Spark   038/060
Devolution Spray Z I Unbroken Bonds   166/214 Full Metal Wall   044/054
Celebi   Unified Minds   4/236 Miracle Twin   003/094
Aerodactyl         Pokémon Card 151   142/165