Pokémon that cannot be traded Pokémon GO include most Mythical Pokémon and any Pokémon that has already been traded once. Other temporary states can also block a trade, while Shiny, Legendary, Ultra Beast and unregistered Pokémon are usually Special Trades rather than completely untradeable.
Mythical Pokémon are generally blocked
The clearest Pokémon that cannot be traded Pokémon GO rule covers Mythical Pokémon such as Mew.
Most Mythicals cannot be selected for trading at all. There are limited exceptions in the wider game, so check the current trade screen rather than assuming every species with unusual rarity follows the same rule.
A greyed-out Mythical normally means the restriction is intentional.
Pokémon can only be traded once
A Pokémon received in a trade cannot be traded again.
This is one of the most important Pokémon that cannot be traded Pokémon GO restrictions because there is no undo button and no way to pass a Pokémon around a group.
Before confirming a valuable trade, both Trainers should understand that the Pokémon cannot later be returned to its original owner.
Shadow Pokémon cannot be traded
Shadow Pokémon must be Purified before they become eligible for normal trading rules.
That makes active Shadows part of the Pokémon that cannot be traded Pokémon GO list even when the species itself is normally tradeable.
Purifying changes the Pokémon permanently, so do not do it solely for a trade unless you genuinely want the Purified form.
Some active special forms are blocked
Pokémon that are currently in special combined states can be untradeable. Fused Pokémon, for example, cannot be traded while the Fusion is active.
Current Mega-Evolved states and other temporary transformations may also need to end before the base Pokémon can be used normally.
Pokémon that cannot be traded Pokémon GO often become eligible again once the temporary state is removed, unlike a once-traded Pokémon.
Favorites and Gym defenders
A Pokémon marked as a Favorite is protected from accidental actions and may need to be unfavorited before trading.
Pokémon currently defending a Gym also need to return before they can be managed normally.
These are practical locks rather than permanent Pokémon that cannot be traded Pokémon GO categories.
Check the Pokémon’s status before assuming the species itself is restricted.
Special Trade does not mean untradeable
Legendary Pokémon, Shiny Pokémon, Ultra Beasts, new Pokédex entries, many special forms and Pokémon with unique features can require a Special Trade.
That usually means a higher Stardust cost and a daily Special Trade limit.
They are not automatically Pokémon that cannot be traded Pokémon GO. If the game calls the transaction Special, it can still proceed when both Trainers meet the requirements.
Pokémon tied up in other systems
A Pokémon may also be unavailable because it is assigned to a Gym, is currently your Buddy in a state that blocks the action, is involved in a special transformation or needs another temporary status cleared first.
These situations are worth checking before changing anything permanent. A greyed-out Pokémon does not always mean its species is globally forbidden from trading.
Trainer level matters
Trading is available from Trainer level 10.
A lower-level account cannot use the trading system normally, so the problem may be the Trainer rather than the selected Pokémon.
Child accounts can also depend on social permissions controlled through the relevant parent system.
Pokémon that cannot be traded Pokémon GO searches sometimes come from account restrictions rather than Pokémon restrictions.
Remote Trade rules do not remove species restrictions
Forever Friends can earn Remote Trades, allowing a trade without being physically together.
Remote access does not make an otherwise blocked Pokémon eligible.
A previously traded Pokémon is still blocked, and a Mythical that cannot be traded locally does not become legal simply because the Trainers have a Remote Trade available.
Check the trade screen before changing anything
If a Pokémon is greyed out, read the message shown by the game.
Do not Purify, unfavorite, unfuse or otherwise alter a rare Pokémon until you know which restriction is actually responsible.
The permanent Pokémon that cannot be traded Pokémon GO rules are relatively simple: most Mythicals cannot trade, and anything already traded cannot trade again. Many other greyed-out states are temporary or are Special Trade requirements rather than permanent bans.
Official site: Pokémon GO
