We present a comprehensive study of the anisotropic optical properties of nonpolar GaN/AlGaN multiple quantum wells intentionally designed to act as an active region of a planar microcavity operating in the strong-coupling regime. The strain induced by the underlying AlGaN-based Bragg reflector leads to a redistribution of exciton oscillator strength as revealed by photoluminescence and reflectivity measurements. Complementary k . p calculations show an excellent agreement with experiments and emphasize the opportunity to tune the nature of the light-matter coupling in a microcavity by means of strain engineering. Finally, the validity of the developed model is proven by angle-resolved photoluminescence studies carried out on the complete microcavity structure. The recorded eigenmode spectra reveal the coexistence of the weak- and the strong-coupling regime along the two orthogonal polarization planes.