Games like Up Island
Games like Up Island include Pizza Tower, Shelldiver, SANABI, Hollow Knight, and Celeste. We matched them by the tags players give Up Island on Steam (Casual, Singleplayer, Action, 2D, and Platformer): closest matches first, and among equally close ones the better-known games.

Pizza Tower
Shared: 2D Platformer · Singleplayer · Platformer

Shelldiver
Shared: Casual · Incremental · 2D

SANABI
Shared: Action · Singleplayer · 2D Platformer

Hollow Knight
Shared: Platformer · 2D · Singleplayer

Celeste
Shared: Platformer · Singleplayer · 2D Platformer

Katana ZERO
Shared: Action · Platformer · 2D Platformer

Zup! S
Shared: Casual · 2D · Singleplayer

Timberman
Shared: Casual · Action · Singleplayer

Skul: The Hero Slayer
Shared: Action · 2D · Singleplayer

Super Meat Boy
Shared: Platformer · Singleplayer · 2D Platformer

ANTONBLAST
Shared: Action · 2D · Singleplayer

Russian Life Simulator
Shared: Singleplayer · 2D · Action

Oozi: Earth Adventure
Shared: Casual · Platformer · 2D Platformer

Webbed
Shared: 2D Platformer · 2D · Cute

Ori and the Will of the Wisps
Shared: Singleplayer · Platformer · Action

Sonic Superstars
Shared: Action · Casual · Platformer

Planet of Lana
Shared: Action · Singleplayer · 2D Platformer

Twin Shot Deluxe
Shared: Casual · Action · 2D Platformer

BEEP
Shared: Singleplayer · Platformer · 2D

Sonic Origins
Shared: Action · 2D Platformer · Casual

Gensokyo Night Festival
Shared: Action · Casual · Indie

Brawlhalla
Shared: Casual · 2D Platformer · Platformer

Gravity Circuit
Shared: Action · Platformer · Singleplayer

DJMAX RESPECT V
Shared: Casual · Action · Singleplayer