The gameplay in Sega Superstars Tennis is similar to Sega's Virtua Tennis series, with characters able to perform techniques such as lob shots and drop shots. Characters each have different statisticts and proficiency in specific areas, such as power or control. Each character also has their own unique "Superstar State", a special ability that can be activated once an accompanying meter is filled. The effects of a Superstar State vary depending on the character; for example, Sonic transforms to Super Sonic and causes the ball to zig-zag when hit, while Gilius summons thunderbolts that can temporarily stun opponents. The game features 10 courts themed after various Sega games, such as Green Hill Zone from Sonic the Hedgehog and Shibuya Downtown from Jet Set Radio.
Sega Superstars Tennis features several gameplay modes. Superstars mode allows the player to complete various missions themed around a specific Sega games, which take the form of exhibition matches, tournaments and minigame score challenges; completing these missions will unlock new areas based on other games with additional sets of missions to complete. Players will unlock new additional characters, courts, and music for use in gameplay as they progress through Superstars. Match mode offers standard tennis gameplay in singles or doubles matches for up to four players locally, while Tournament mode allows a single player to compete in a series of five sequential matches against random computer opponents. There are also several playable minigames that feature alternate gameplay styles inspired by other Sega games, including Space Harrier, Puyo Pop Fever, ChuChu Rocket!, and Virtua Cop. The PlayStation 3 and Xbox 360 versions also support online multiplayer.
The Wii version features support for three different control schemes: the Wii Remote with Nunchuk, the Wii Remote sideways, and the Classic Controller. The Nintendo DS version of the game can be played with the standard control pad or the touch screen.
Sega Superstars Tennis features 16 playable characters originating from eight different Sega franchises. Eight characters are available from the start, while the remaining eight must be unlocked through Superstars mode. The game marks the first 3D appearances of both Alex Kidd (Alex Kidd) and Gilius Thunderhead (Golden Axe) in a video game, and marks Alex Kidd's first playable appearance in eighteen years following the 1990 release of Alex Kidd in Shinobi World.