Partner Pokémon are special Pokémon that the player have as their Starters in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!. The Partner Pokémon in those games are Pikachu and Eevee. The Partner Pokémon are also the ones to use Secret Techniques and exclusive moves in those games. Unlike their regular kinds, the Partner Pokémon are special as they only share their feelings with the player. The Partner Pokémon can only be the starters of the player in the game that they are received in, Partner Pikachu can only be received in Pokémon: Let's Go, Pikachu!, while Partner Eevee can only be received in Pokémon: Let's Go, Eevee!.
While the player can capture and train other Pikachu and Eevee in both games, the partner Pokémon have various special differences from their typical variants.
- The game-exclusive Partner the player starts with cannot be traded to other games, as they are only exclusive to Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!.
- The Partner Pokémon will stay out of their Poké Ball, a game mechanic that was originally exclusive to Pikachu in the original Pokémon Yellow game. The Partner Pokémon will ride on the player's character.
- The Partner Pikachu are constantly seen riding on the player's shoulder while Partner Eevee are constantly seen riding on top of the player's head, even when not in the active party.
- The Partner Pokémon will also have no interest in evolving in these games.
- The Partner Pokémon can also wag their tail to indicate that a hidden item is located in front of the player.
- The Partner Pokémon have higher base stats, and are fixed to join the party with a fixed all-perfect 31 IVs in every stat, but cannot be Shiny. Their gender can be also determined by the title screen during the start of the game.
- The partner Pokémon can perform Secret Techniques that take the place of HMs. These Techniques do not take up a slot in the move set, nor are they moves intended for battle.
- The player's partner can be interacted with and fed, similar to Pokémon-Amie and Pokémon Refresh in previous games, which can be done by using Partner Play on the menu.
- The Partner Pokémon can also be dressed in different outfits, including sets made to match the player, and be given different hairstyles when pet in certain ways in the Switch's handheld mode.
- Female Partner Eevee have a special heart-shaped pattern around the tip of their tail. This trait was later introduced to normal female Eevee in Generation VIII as a gender difference.
- They have larger models than their regular counterparts.
- Partner Eevee's coat is lighter shade of brown compared to its regular counterpart and it has purple irises rather than brown.
These are the Exclusive Moves that only the Partner Pokémon can use. They can learn them via Move Tutor, and can activate partner powers in battle once they have high enough friendship. The Partner Pokémon's Exclusive Moves cannot be used in other games, as they are only exclusive to Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!.
- Splishy Splash: A Water-type Move. The user charges a huge wave with electricity and hits the opposing Pokémon with the wave. This may also leave the opposing Pokémon with paralysis.
- Floaty Fall: A -type Move. The user floats in the air, and then dives at a steep angle to attack the target. This may also make the target flinch.
- Zippy Zap: An Electric-type Move. The user attacks the target with bursts of electricity at high speed. This move always goes first and results in a critical hit.
- Pika Papow: An Electric-type Move. It's the Partner's special power. The more Pikachu loves its Trainer, the greater the move's power. It never misses. It requires a special level of Friendship in order to be activated.
- Veevee Volley: A Normal-type Move. It's the Partner's special power. The more Eevee loves its Trainer, the greater the move's power. It never misses. It requires a special level of Friendship in order to be activated.
- Bouncy Bubble: A Water-type Move. The user attacks by shooting water bubbles at the target. It then absorbs water and restores its HP by half the damage taken by the target.
- Buzzy Buzz: An Electric-type Move. The user blasts a jolt of electricity to attack the target. This can also leave the target with paralysis.
- Sizzly Slide: A Fire-type Move. The user ignites itself in flames and charges at the target. This can also leave the target with a burn.
- Glitzly Glow: A Psychic-type Move. The user bombards the target with telekinetic force. A wondrous wall of light is put up to weaken the power of the opposing Pokémon's special moves.
- Baddy Bad: A Dark-type Move. The user acts bad and attacks the target. A wondrous wall of light is put up to weaken the power of the opposing Pokémon's physical moves.
- Sappy Seed: A Grass-type Move. The user grows a gigantic stalk that scatters seeds to attack the target. The seeds drain the target's HP every turn.
- Freezy Frost: An Ice-type Move. The user attacks with a crystal made of cold frozen haze. It eliminates every stat change among all the Pokémon engaged in battle.
- Sparkly Swirl: A Fairy-type Move. The user attacks the target by wrapping it with a whirlwind of an overpowering scent. This also heals all status conditions of the user's party.
The Partner Pokémon hasn't appeared yet in the anime, but there are some elements of Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! that can be seen in the anime.
- Ash's Pikachu is always reluctant to stay inside it's Poké Ball, and has always been seen riding on Ash's head or shoulder during his journey. Pikachu also refuses to evolve and wants to keep on growing stronger as the way it is.
- Risa caught an Eevee in The Power of Us, which became her starter.
- Pikala has a bunch of Pikachu with different hairstyles that are identical to the hairstyles of the Partner Pokémon.
- Lana caught an Eevee, nicknamed Sandy who wears a hairstyle similar to the ones that can be given to the partner Pikachu and Eevee. Sandy also knows how to Mantine Surf, similar to one of the Secret Techniques the Partner Pokémon knows which is Sea Skim.
- Despite Partner Pikachu and Eevee being special versions than their regular counterparts, neither of them are classified in the Pokédex as unique forms.
- The Signature Moves of the Partner Pokémon in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! are the only moves that can't be used in other games.
- They are also the only moves introduced in Let's Go, Pikachu! and Let's Go, Eevee! to have been used in the anime.
- Partner Eevee has more exclusive moves than Partner Pikachu in these games.
- Interesting enough, Partner Eevee's exclusive moves has the same types as its Evolution forms does.
- Notably, Pikachu and Eevee capable of Gigantamax can be received in Pokémon Sword and Shield if the player has save data of Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!, respectively. Pikachu and Eevee capable of Gigantamax cannot evolve, which is similar to the Partner Pokémon from Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!.