Sonic the Hedgehog: Pocket Adventure is the only Sonic the Hedgehog game released for the Neo Geo Pocket Color. It was released on December 3, 1999 in North America, and on January 11, 2000 in Japan. It was the second Sonic game to be released on a console not developed by Sega (the first being Sonic Jam for the Game.com). Sonic the Hedgehog: Pocket Adventure was developed by Dimps and Sonic Team, and published by SNK and Sega. Despite having very similar levels and gameplay as Sonic the Hedgehog 2, it contains arrangements of music from Sonic the Hedgehog 3 & Knuckles.
Sonic the Hedgehog: Pocket Adventure has the same traditional gameplay that most other Sonic games have. The gameplay is similar to that of the original three Sonic games, but the art style is more representative of the Sonic Advance games. During the game, there are several zones that the player must navigate (each with a boss).
Sonic the Hedgehog: Pocket Adventure also has a multiplayer mode for up to two players. Each player must have a Neo Geo Pocket Color, a copy of the game, as well as a link cable. The multiplayer game is known as Duel Mode, with two different modes: Sonic Rush and Get the Rings. Sonic Rush has the two players racing to the end of a level, while Get the Rings has the players trying to get an amount of rings. The second player gets to play as Tails, which is unique, as Sonic is the only playable character in the single-player game.
- Neo South Island - Neo South Island is a zone which is largely inspired by Green Hill Zone from the original Sonic the Hedgehog. Despite being based on the Green HIll Zone level, it does contain things from the Emerald Hill level in Sonic the Hedgehog 2 and from the Palmtree Panic level in Sonic CD.
- Secret Plant - Secret Plant is based on Chemical Plant Zone, from Sonic the Hedgehog 2. The level has enemies and such from Sonic the Hedgehog 2.
- Cosmic Casino - Cosmic Casino is a zone that is based on Sonic the Hedgehog 2's Casino Night Zone, in which the player navigates a large, casino filled with bumpers, enemies, and more.
- Aquatic Relix - Another zone that is based off of a Sonic the Hedgehog 2 zone. This time, it is based on Aquatic Ruin Zone. It is of note that this and Secret Plant are the only levels in the game to contain underwater portions.
- Sky Chase - Sky Chase is a zone that is inspired by Sky Chase Zone in Sonic the Hedgehog 2. In this zone, Sonic rides on the wings of the Tornado (Tails' airplane).
- Aerobase - Aerobase is a zone that is also based on a level from Sonic the Hedgehog 2 titled Wing Fortress Zone. It takes place on a huge, flying warship.
- Gigantic Angel - Gigantic Angel has a background design that is taken from the original Sonic the Hedgehog's Scrap Brain Zone. It also is filled with obstacles and traps that are taken from Metropolis Zone in Sonic the Hedgehog 2.
- Last Utopia - Last Utopia is a battle between Sonic and Dr. Robotnik. Dr. Robotnik flies around in a large vehicle, while Sonic fights him.
- Chaotic Space - Chaotic Space is a bonus zone that isn't technically based off of any other zone, but rather plays similarly to Doomsday Zone from Sonic & Knuckles.