Beatmania IIDX 9th style is one of the many titles in Konami's IIDX rhythm game series, featuring more than 80 tracks, primarily from the arcade version of the same title. As usual for the beatmania series, the player is given seven piano keys and a turntable, and must play along with the notes that scroll down the screen to play the music. 9th style features a completely revamped interface compared to the previous titles, owing to the more powerful hardware that the arcade version ran on.

There are three main modes: Arcade mode tasks the player with completing several tracks in succession, Free mode lets the player freely play any unlocked song, and Training mode lets the player practice parts of songs without danger of failure. The Beginner's mode from 5th style and the Class mode from 7th style are also present, as is the gallery mode.