The vectorial evolution of light polarization can reveal the microstructure and anisotropy of a medium beyond what can be obtained from measuring light intensity alone. However, polarization imaging in reflection geometry, which is ubiquitous and often preferred in diverse applications, has often suffered poor and even incorrect characterization of anisotropic media. Here, we present reciprocal polarization imaging of complex media in reflection geometry with reciprocal polar decomposition of backscattering Mueller matrices enforcing reciprocity. We demonstrate that reciprocal polarization imaging of complex chiral and anisotropic media accurately quantifies their anisotropic properties in reflection geometry, whereas traditional approaches encounter difficulties and produce inferior and often erroneous results from the violation of reciprocity. In particular, reciprocal polarization imaging provides consistent characterization of complex media of different thicknesses, accurately measures the optical activity and glucose concentration of turbid media in reflection, and discriminates between cancerous and normal tissue with even stronger contrast than forward measurement. Reciprocal polarization imaging promises broad applications of polarization optics ranging from remote sensing to biomedicine in reflection geometries, especially in in vivo biomedical imaging, where reflection is the only feasible geometry.