The games were announced worldwide on May 30, 2018, at a Pokémon press conference in Tokyo, Japan. The paired versions were released worldwide on November 16, 2018. All copies of the game are playable in nine languages: Japanese, English, German, Spanish, French, Italian, Korean, and Simplified and Traditional Chinese.
The Joy-Con is used to catch Pokémon by flicking one's wrist in a throwing motion, similar to the method in Pokémon GO. While in handheld mode, wild Pokémon are caught by aiming the Poké Ball with motion controls. Wild Pokémon, except for interactive Pokémon, can no longer be battled in a traditional sense, but NPC Trainers can be battled as normal.
Two-player simultaneous play feature, which can be done by sharing one of the Joy-Con controllers. Both players can adventure at the same time and one of them may lend a hand by joining in battles against NPC Trainers. This feature also increases the chances of catching Pokémon successfully by throwing Poké Balls together at the wild Pokémon.
An accessory called the Poké Ball Plus can be used to catch Pokémon in place of a Joy-Con. Like the Pokéwalker, a Pokémon can be taken on the go and be interacted with for rewards when returned to the game. It also contains the Mythical PokémonMew, a special Pokémon that cannot be obtained by normal gameplay.
The introduction of two new Mythical Pokémon: Meltan and its evolved form, Melmetal.
Once the player has become the Champion, Master Trainers will appear and can be found scattered throughout the Kantoregion. They are considered the strongest Trainers for every Pokémon species in Generation I and can be spotted by the icon of the Pokémon they favor above their heads. In these battles, the player are only allowed to use one Pokémon which is the same species as them and any medicines are prohibited.
The games are no longer backwards compatible with any other main series games, unlike every other main series game released since Pokémon FireRed and LeafGreen.
In addition to customizing the player's color skin and clothing, the starter Pokémon can also be dressed in different outfits and be given different accessories and hair styles.
Wild Pokémon now appear on the overworld. Coming into contact with one will engage them. They may appear with either a red or blue aura, which indicates their size, either being larger or smaller, respectively, than their own standard size. Similar to the previous games, there is a chance to encounter Shiny Pokémon in the wild.
A feature called the Catch Combo tracks how many of the same species of Pokémon is caught in a row without the Pokémon running away or the game turning off. The higher the combo, the stronger and rarer wild Pokémon become, and Shiny Pokémon become more common.
High friendship can boost all stats by up to 10%, before adding in AVs.
The Bicycle, one of the key items in Generation I and III, has been removed; the Miracle Cycle shop in Cerulean City is replaced with the home of a Bike Maniac who just collects many kinds of bikes; and the Cycling Road is redesigned as the "Pokémon Road" without any Bikers or Roughnecks challenging the player.
A unique section of the Bag called the Candy Jar is used for increasing the stats of Pokémon by giving them various types of Candy obtained from transferring Pokémon to Professor Oak, similar to the Candy from Pokémon GO.
A section in the bag called the Pokémon Box replaces PCs, allowing players to switch the Pokémon in their party at any point in the game.
The player can no longer play mini-game on the machines in the Celadon Game Corner because the service desk has run out of coins. However, there are certain spots where the hidden items such as Bottle Caps are recurring once per day in the Game Corner.
The Safari Zone in Fuchsia City replaces the zoo, and has added the GO Park, where the player is able to interact with their caught Pokémon. Similar to the Box system in the Pokémon Storage System, the GO Park complex has a total of 20 GO Parks, with each capable of holding 50 Pokémon. Thus, the player can transfer up to 1,000 Pokémon into the games.
If the player has gathered 25 of the same species of Pokémon, they can play a minigame in the Park's Play Yard for Candy. Alolan forms are counted as a separate species, listed in red.
The starter Pikachu and Eevee can activate their own partner powers in battle once they have high enough friendship. If activated while they are in battle, they use an exclusive move—Pika Papow or Veevee Volley—which increases in damage based on friendship. If activated while they are not in battle, they boost the stats of the current Pokémon.
TMs have been reordered and readded with some moves that previously available as Move Tutor. The amount of TM moves available also have been decreased compared to previous core series games.
HM moves have been replaced by Secret Techniques that the starter Pikachu and Eevee can use in the overworld, but do not take up move slots. These include Chop Down for Cut, Sea Skim for Surf, and Sky Dash for Fly.
Interactive Pokémon such as Electrode, Snorlax, and Legendary Pokémon can be battled, but they must be defeated to be captured. A five-minute time limit is in effect for the battle. If the timer hits 0, the battle ends abruptly. Hitting the Home button or putting the console in sleep mode does not pause the timer.
Electrode disguised as items are now white on top and red at the bottom, just like real Electrode.
Both Snorlax are battled with either an Attack or Defense stat boost, while all the Legendary Pokémon have all their stats increased, similar to Totem Pokémon.
The starter Pikachu and Eevee also react differently near the hidden items by wagging their own tail.
A feature that allow the player to pet a Pokémon similarly to Pokémon-Amie and Pokémon Refresh, can be called by pressing "Play with Pikachu/Eevee" on the menu. However, this feature is limited to the starter Pikachu and Eevee.
Only Gyarados and Lapras cannot appear outside unless they are in the sea.
After entering the Hall of Fame for the first time, Charizard, Aerodactyl, and Dragonite can be ridden across the Kanto region; however they cannot enter the secluded places. This allows the player to encounter and catch the wild Pokémon in the sky.
Blue appears early in the Pewter City and later in the Silph Co. during the raid of Team Rocket. Similar to the storyline prior to Generation II, Blue takes over as the Gym Leader of Viridian Gym after the player beats the Champion.
The game-exclusive Partner the player starts with cannot be traded to other games. While a single Persian is obtainable in Let's Go, Pikachu!, and a single Arcanine is obtainable in Let's Go, Eevee! through an NPC, they are not obtainable as wild Pokémon in those respective games.
Each time a Pokémon is transferred from Pokémon GO to the Nintendo Switch, the Pokémon GO account will be awarded 100 expereince and one candy corresponding to each Pokémon transferred. Transferring a Pokémon from Pokémon GO to the Switch for the first time also gives the GO account a Mystery Box, which can be opened once every seven days to spawn wild Meltan. Each time before the box can be opened, a Pokémon transfer must be made from Pokémon GO to the Nintendo Switch.
Gaming magazine Famitsu gave Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! a score of 37 out of 40. IGN rated the games a "Great" 8.3/10. Let's Go, Pikachu! and Let's Go, Eevee! hold a rating of 77.49% and 79.31%, respectively, on GameRankings.
Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! sold 661,240 units on their first week on the Japanese market.
Because South Korea never got an official Korean-language release for either Generation I or Generation III games (and thus never received Pokémon Red and Green nor Pokémon FireRed and LeafGreen), these games are the first Korean-language games which primarily feature Kanto and follow the original story featured in Generation I.
However, Kanto was still accessible in both Generation II's Pokémon Gold and Silver—which was the first official Korean-language release of any Pokémon game—and its Generation IV remake, Pokémon HeartGold and SoulSilver, albeit as a post-game extra. Therefore, Let's Go, Pikachu! and Let's Go, Eevee! are the first games in Korean to start in Kanto.
The same holds true for the players in Greater China, although this is the first official Chinese-language games to visit Kanto in any form.