"We Can't Stop" is a mid-tempo pop, R&B and electropop song. It is written in the key of E major with a tempo of 80 beats per minute in common time, and Cyrus' vocals span two octaves, from the low note of B2 to a high F5. The song follows the chord progression E–Gm–Cm–A (I–iii–vi–IV). The track also includes a sample of the track "La Di Da Di" by Doug E. Fresh and MC Ricky D. John Kennedy of Vibe compared the track to the works of Rihanna.
