Optical anisotropy measurement is essential for material characterization and biological imaging. In order to achieve single‐shot mapping of the birefringence parameters of anisotropic samples, a novel polarized light imaging concept is proposed, namely quantitative polarization interference microscopy (QPIM). QPIM can be realized through designing a compact polarization‐resolved interference microscopy system that captures interferograms bearing sample's linear birefringence information. To extract the retardance and the orientation angle maps from a single‐shot measurement, a mathematical model for QPIM is further developed. The QPIM system is validated by measuring a calibrated quarter‐wave plate, whose fast‐axis orientation angle and retardance are determined with great accuracies. The single‐shot nature of QPIM further allows to measure the transient dynamics of birefringence changes in material containing anisotropic structures. This application is demonstrated by capturing transient retardance changes in a custom‐designed parallel‐aligned nematic liquid crystal‐based device.