An acoustic wave device includes a piezoelectric layer, an IDT electrode, a high-acoustic-velocity support substrate, and a low-acoustic-velocity film. The high-acoustic-velocity support substrate is located on an opposite side of the piezoelectric layer from the IDT electrode in the thickness direction of the piezoelectric layer. The low-acoustic-velocity film is disposed between the high-acoustic-velocity support substrate and the piezoelectric layer in the thickness direction. The high-acoustic-velocity support substrate includes a base region and a surface region disposed nearer to the low-acoustic-velocity film than the base region in the thickness direction and whose crystal quality is worse than that of the base region. The surface region includes first and second layers disposed nearer to the base region than the first layer in the thickness direction and whose crystal quality is better than that of the first layer.