Kirby and the Rainbow Curse is a follow-up to the 2005 DS game Kirby: Canvas Curse with similar gameplay. One day, a rift opens in the sky and sucks out all colour from Dream Land on the planet Pop Star. Elline, a paintbrush fairy from Seventopia, manages to dash through the rift and uses her powers to bring back colour to Kirby and Waddle Dee. She explains that a former friend, Claycia, has used the colours to create seven worlds. The three move through the rift with Kirby as the main protagonist to bring back home colour.

Just like in Canvas Curse Kirby moves around in ball form. Each world consists of several levels and Kirby still cannot be controlled directly. Instead the player has to help him by drawing rainbow coloured lines/ropes as platforms, slides and loops quickly in succession to help him get around. These are drawn on the Game Pad's touch screen and appear permanently on the screen. Drawing is limited through a rainbow gauge in the top left corner that regenerates slowly. A spinning attack to defeat enemies or gain some extra speed while moving is triggered by touching Kirby. Copying abilities by hitting enemies does not return in this game. Levels are filled with stars and for every 100 stars collected a star dash can be performed, a charged attack with more power, speed and range as Kirby grows. These star dashes, shown through a cyan ring orbiting Kirby, do not need to be used right away, but can be saved for later. They can for instance be used to break through indestructible blocks. Other game elements include drawing rainbows to block water or lava, but often only temporary. There are also gray zones where it is impossible to draw. Levels have bottles that fill up the rainbow meter and extra lives. Kirby has four hit points by default.

There are bosses at the ends of the worlds and many levels have environment based puzzles, for instanced based on locating and transporting keys to unlock barriers. Levels have secret treasure chests that are accessed by solving puzzles or clearing a timed sequence. Treasure chests are revealed by collecting puzzle pieces. Just like in Kirby's Epic Yarn there are sections where Kirby can transform. In this game he can become a rocket, a tank and a submarine, with different controls and gameplay, as well as ranged weapons, to advance through the levels. The game supports cooperative games where up to three local players control Bandana Waddle Dees on the TV using Wii Remotes. These Waddle Dees have two hit points and are able to carry and throw Kirby and have a charged attack. When Kirby transforms they also receive new weapons. In cooperative games the evil hand from the rift sometimes appears and attempts to capture Kirby and only the Waddle Dees can prevent this. At the end of levels a rotating goal gate appears where a prize can be won.

The games visual style resembles a claymation look. Unlockables include clay figures, music tracks and pages of Elline's diary. The main story mode consists of 28 levels and the challenge mode (short challenges to earn medals) has more than 40. The game is compatible with the amibo figures King Dedede, Kirby and Meta Knight. They provide two hit points, an extra star dash per day, and more speed while doing a spinning attack respectively.