An acoustic wave device includes a support including a support substrate, a piezoelectric layer on the support, and an IDT electrode on the piezoelectric layer and including busbars and electrode fingers. In plan view when viewed in a lamination direction of the support and the piezoelectric layer, an acoustic reflector overlaps at least a portion of the IDT electrode on the support. When a thickness of the piezoelectric layer is defined as d and a center-to-center distance between the electrode fingers adjacent to each other is defined as p, d/p is about 0.5 or smaller. Mass addition films are located over at least one of pair of edge regions and a gap region adjacent to the edge region and aligned in an electrode finger facing direction. The mass addition films are not located on at least a portion between the adjacent electrode fingers.