Maximum of 200 friends can be added to your Pokémon GO Friends List

Pokémon GO has introduced social and trading features that allow Trainers to connect with each other by adding friends, sending Gifts and participating in a new Friendship level system that unlocks bonuses. These brand-new features are now available for all players. Adding Pokémon GO Friends was initially only available for players who are at a Level 40 standing. However, friends and gifting are now live for all players of all levels. Meanwhile, trading is now available for all players level 10 and above. A maximum of 200 friends can be added to your Pokémon GO Friends List.

Source: @PokemonGoApp