An acoustic wave device includes: a substrate; a piezoelectric film located on the substrate; a lower electrode and an upper electrode facing each other across at least a part of the piezoelectric film; a silicon oxide film located at an opposite side of at least one of the lower electrode and the upper electrode from the piezoelectric film; a first insulating film that is located between the at least one of the lower electrode and the upper electrode and the silicon oxide film and includes a non-oxygen-containing material; and an additional film located at an opposite side of the silicon oxide film from the first insulating film and made of a material different from a material of the silicon oxide film and a material of the first insulating film.