There are 26 trade evolutions in the main series from regular forms, plus Alolan Graveler into Alolan Golem. Sixteen of those need a held item, eight need only a trade, and two (Karrablast and Shelmet) must be traded for each other.
Each row below gives what the trade needs and the generation that trade evolution began in.
The full list
Trade evolution started in Generation 1 with Kadabra, Machoke, Graveler and Haunter. Held-item trade evolutions began in Generation 2. When the trade finishes, the item is used up.
| Pokémon | Evolves into | Needs | Trade method since |
|---|---|---|---|
| Kadabra | Alakazam | nothing, just trade | Gen 1 |
| Machoke | Machamp | nothing, just trade | Gen 1 |
| Graveler | Golem | nothing, just trade | Gen 1 |
| Haunter | Gengar | nothing, just trade | Gen 1 |
| Poliwhirl | Politoed | holding King's Rock | Gen 2 |
| Slowpoke | Slowking | holding King's Rock | Gen 2 |
| Onix | Steelix | holding Metal Coat | Gen 2 |
| Seadra | Kingdra | holding Dragon Scale | Gen 2 |
| Scyther | Scizor | holding Metal Coat | Gen 2 |
| Porygon | Porygon2 | holding Upgrade | Gen 2 |
| Clamperl | Huntail | holding Deep Sea Tooth | Gen 3 |
| Clamperl | Gorebyss | holding Deep Sea Scale | Gen 3 |
| Rhydon | Rhyperior | holding Protector | Gen 4 |
| Electabuzz | Electivire | holding Electirizer | Gen 4 |
| Magmar | Magmortar | holding Magmarizer | Gen 4 |
| Porygon2 | Porygon-Z | holding Dubious Disc | Gen 4 |
| Dusclops | Dusknoir | holding Reaper Cloth | Gen 4 |
| Feebas | Milotic | holding Prism Scale | Gen 5 |
| Boldore | Gigalith | nothing, just trade | Gen 5 |
| Gurdurr | Conkeldurr | nothing, just trade | Gen 5 |
| Karrablast | Escavalier | traded for Shelmet | Gen 5 |
| Shelmet | Accelgor | traded for Karrablast | Gen 5 |
| Spritzee | Aromatisse | holding Sachet | Gen 6 |
| Swirlix | Slurpuff | holding Whipped Dream | Gen 6 |
| Phantump | Trevenant | nothing, just trade | Gen 6 |
| Pumpkaboo | Gourgeist | nothing, just trade | Gen 6 |
Clamperl is the one Pokémon with two outcomes: it becomes Huntail with a Deep Sea Tooth and Gorebyss with a Deep Sea Scale. In this list, Porygon is the only line with two trade steps in a row: it becomes Porygon2 with an Upgrade, then Porygon-Z with a Dubious Disc.
The 14 held items are King's Rock, Metal Coat, Protector, Dragon Scale, Upgrade, Dubious Disc, Electirizer, Magmarizer, Prism Scale, Reaper Cloth, Deep Sea Tooth, Deep Sea Scale, Sachet and Whipped Dream. Two items are used twice: King's Rock (Poliwhirl and Slowpoke) and Metal Coat (Onix and Scyther).
Trade evolutions by generation
Counting the rows in the table: 4 trade evolutions started in Generation 1, 6 in Generation 2, 2 in Generation 3 (both are Clamperl), 5 in Generation 4, 5 in Generation 5 and 4 in Generation 6. The only later one is Alolan Graveler, from Generation 7.
By item, Generation 2 brought King's Rock, Metal Coat, Dragon Scale and Upgrade. Generation 3 added Deep Sea Tooth and Deep Sea Scale. Generation 4 added Protector, Electirizer, Magmarizer, Dubious Disc and Reaper Cloth. Generation 5 added Prism Scale for Feebas, and Generation 6 added Sachet and Whipped Dream.
Special cases
Karrablast and Shelmet evolve only when they are traded for each other. Trade a Karrablast to a friend for their Shelmet and both evolve.
Feebas used to evolve only with a high Beauty stat. From Generation 5 it can also evolve by trade while holding a Prism Scale.
Alolan Graveler evolves into Alolan Golem by trade, like the regular form.
You cannot cancel a trade evolution with the B button. An Everstone stops it, with one exception: Kadabra outside Generations 2 and 3 always evolves, even holding one.
Evolving without a trade
In Legends: Arceus you do not need to trade. A Linking Cord does the job. Pokémon that need a held item in other games evolve when you use that item on them. Pokémon that need only a trade use the Linking Cord too.
A trade still needs a second console or a friend in most other games. If you are helping a younger player, the parents' guide explains how trading works. Items such as these are listed in the items guide.
Trade evolution in Pokémon GO
Pokémon GO added trade evolution on 10 January 2020. A Pokémon you got in a trade evolves for 0 Candy. Pokémon that need a held item in the main series use Evolution items in GO instead of trading. Not every trade evolution from the main games can trade evolve in GO yet.
Other ways to evolve
Not every evolution needs a trade. Eevee has eight evolutions, the most of any Pokémon: see the Eevee evolutions. For the general rules (level, stone, friendship and more), read how Pokémon evolution works. Every stone and evolution item has its own list on the evolution items page. Regional forms like Alolan Graveler have their own guide in the regional forms list.