The Boost Star is a type of Star that first appears in New Super Mario Bros. U. Unlike the other Stars, they can only collected in Boost Mode. The Boost Star appears when if the players using the Wii Remotes steps ten Boost Blocks that still have their symbols on them, filling the meter only. If the meter on the top of the screen of Boost Mode is filled, they will appears. If a player having the GamePad, taps on the Boost Star, the player can instantly short time defeat enemies and tapping them by break blocks with the stylus or the finger like with the Starman. Koopa Troopas, Thwomps, and King Bills, can only be defeated by this method.
The star is purple on the GamePad. It can not be activated by any playable or unlockable character, is almost invisible with an slight blue outline.