Ninja UP! is a vertically oriented platform game similar to PapiJump and Doodle Jump. The player controls a ninja who needs to go as high as possible. This is done by drawing a line underneath him. Once drawn, it changes into a rope that has a trampoline effect, launching the ninja upwards. When the ascent slows down, a new line needs to be drawn and so on. The sides of the screen can be used to bounce around. The player is also rewarded for drawing small lines instead of long ones, as the first give the ninja a boost and launch him much higher.
Along the way various obstacles and enemies are encountered such as flying ninjas and UFOs. A single hit is deadly and means the game needs to be started over. The same applies when the player is too slow to draw or draws in the wrong spot, causing the ninja to fall down. The game is free-to-play and has no in-app purchases. Instead, both picture and video advertisements are regularly shown, along with a banner near the bottom of the screen.