This study presents a non-invasive method for assessing in vitro porcine oocyte maturation using polarized light microscopy and phase-shifting techniques, eliminating the need for chemical staining and minimizing oocyte stress. A custom-built polarized microscopy system with liquid crystal retarders and a polarization camera allowed the measurement of birefringence in key structures (zona pellucida, perivitelline space and cytoplasm). The six-step and four-step phase shifting methods exhibited higher sensitivity to oocyte quality, whereas the Stokes method displayed greater variability. Birefringence changes became significant after 48 hours, indicating maturation. These findings highlight the effectiveness of phase-shifting techniques as reliable tools for enhancing oocyte selection in in vitro maturation procedures.