Polypropylene is susceptible to oxidative degradation due to the presence of tertiary carbon atoms in its chains. Hindered amine light stabilizers (HALS) and Carbon Black (CB) were used to stabilize injection molding grade polypropylene (PP-HALS and PP-CB, respectively). Also, pre-compounded PP and HALS granules (PPHALS) were used to investigate the effect of pre-compounding on degradation. The degradation was conducted in an ultraviolet (UV) light chamber for 0, 600, and 1500 h, simulating the harsh outdoor weather. Tensile behavior of the exposed PP samples was determined. The reductions in the strain at break values of PP-HALS, PP-CB, and PPHALS after 1500 h of UV light exposer were 93%, 82%, and 43%, respectively, which shows a slight better effect of CB over HALS to prevent degradation. Also, it shows improved stability in the pre-compounded sample, PPHALS. Moreover, with a combination of PPHALS and CB, the best UV stability can be reached with just a 10% reduction in the strain at break after 1500 h of UV light exposer. Based on the results, using the precomponded HALS granule and CB masterbatch recomnded for production of injection molded polypropylene parts for out door applications.