Acoustic wave filter and multiplexer

An acoustic wave filter includes: a piezoelectric substrate; series resonators connected in series and located on the piezoelectric substrate, each of the series resonators including first electrode fingers that are arranged with a first duty ratio and excite an acoustic wave; parallel resonators connected in parallel and located on the piezoelectric substrate, each of the parallel resonators including second electrode fingers that are arranged with a second duty ratio and excite an acoustic wave, the second duty ratio in at least one parallel resonator being less than the first duty ratio in at least one series resonator; and a dielectric film that has a temperature coefficient of elastic modulus that is opposite in sign to that of the piezoelectric substrate, is located on the piezoelectric substrate so as to cover the first and second electrode fingers, has a film thickness greater than those of the first and second electrode fingers.