Photo-oxidative degradation of polypropylene/clay multifilament yarns containing different amounts of clay was investigated. These samples and pure polypropylene(PP) multifilametns were exposed to long wavelength radiations(λ > 300 nm) under atmospheric condition of constant temperature and relative humidity. The photo-oxidative stability was studied using FTIR spectroscopy, tensile testing and microscopy. The results indicate that the addition of clay particles decreases the stability of PP/clay composites to photo-oxidative degradation according to comparison with pure PP. From FTIR study and tensile properties, it was also found that the multifilaments with higher clay loading reveals a faster loss of mechanical properties, higher photo-oxidative product formation and more reduction in the induction time of photooxidation. Moreover, the crack formation on surface of irradiated filaments corresponds well to the conclusions in tensile properties and FTIR characterization. These samples and pure polypropylene (PP) multifilametns were exposed to long wavelength radiations (λ> 300 nm) under atmospheric conditions of constant temperature and relative humidity. The photo-oxidative stability was studied using FTIR spectroscopy, tensile testing and microscopy. The results indicate that the addition of clay particles reduces the stability of PP / clay composites to photo-oxidative degradation according to comparison with pure PP. From FTIR study and tensile properties , it was also found that the multifilaments with higher clay loading reveals a faster loss of mechanical properties, higher photo-oxidative product formation and more reduction in the induction time of photooxidation. Moreover, the crack formation on the surface of irradiated filaments accounts for well to the conclusions in tensile properties and FTIR characterization.