This Letter addresses wavefront reconstruction by a retroemission device (REM). REM represents a lenslet array mounted on a substrate made of photoluminescent optical material, such as a polymer film impregnated with upconversion nanoparticles. An excitation light wavefront incident on the REM was sampled by the lenslet array piece-wise. Each wavelet at the lenslet aperture was converged into a voxel in the substrate, with its coordinates encoding the angle of incidence and curvature of the wavelet. Photoluminescence excited in the voxel was radiated isotropically, its back-propagating fraction was captured by the lenslet and transformed into a back-propagating wavelet, which contributed to reproduction of the entire incident wavefront with some fidelity. We experimentally proved the wavefront reconstruction based on REM, and present its theoretical model based on a Fresnel-Kirchhoff approximation.