The quantum effect on the transverse magnetoresistance of degenerate piezoelectric semiconductors with the isotropic parabolic energy bands has been studied for the case where acoustic phonons are the dominant scattering mechanism. The calculation has been performed taking into account the inelasticity in the electron‐phonon scattering due to the finite energy of phonons involved. It is shown that both deformation‐potential and piezoelectric couplings play the same important role for the transverse magnetoresistance in strong magnetic fields B. These results are quite different from those of our previous work for nondegenerate semiconductors in which the acoustic‐phonon scattering due to the piezoelectric coupling contributes very insignificantly to the transverse magnetoresistance. Numerical results also show that transverse magnetoresistances for both couplings oscillate with the magnetic field owing to the degeneracy of the electron gas. However, the number of oscillations will decrease when the magnetic field increases.