Abstract We propose a Mueller matrix ellipsometer based on imaging of the exit pupil of a microscope objective lens. The instrument had a polarizer and a rotating phase retarder on the polarizing arm and a polarizer (analyzer) on the analyzing arm. A vector F representing the optical effect from the objective lens to the detector was obtained by rotating the retarder and analyzing the CCD images taken at multiple azimuths of the retarder. Twelve elements of the Mueller matrix of the sample were determined from the four elements of the F vector. To test this method, a thin film on a cover glass was measured using an oil-immersion objective on internal reflection geometry. The refractive index and thickness of the film were well fitted to a three layer model taking into account the contributions of the objective effect. The accuracy of this system was also evaluated using matrix elements ideally equal to 0 or 1. The random error was estimated from the measured images of the F vector elements to be approximately 0.1% at maximum. The sources of the random and systematic errors inherent to this system were also discussed.