An acoustic wave resonator includes a substrate; a resonating part disposed on a first surface of the substrate and including a first electrode, a piezoelectric layer, and a second electrode; and a cap disposed on the first surface of the substrate and including an accommodating part accommodating the resonating part. The resonating part is configured to be operated by either one or both of a signal output from a first device substrate disposed facing a second surface of the substrate on an opposite side of the substrate from the first surface of the substrate and a signal output from a second device substrate disposed on the cap.