Galbanic acid (GA) is known as an effective photo-sensitizing agent in polyethylene. This paper reports the comparative studies on photo-oxidative degradation of LLDPE films in the presence of varying amounts of galbanic ferric salt (Fe-GA), tetrabromo galbanic acid (Br-GA), GA at the optimum concentration of 0.2% (w/w) and the pure polymer film, exposed to Ultra-Vitalux sun lamp. The degradation rate was monitored through the changes in mechanical properties (retained elongation at break and retained tensile strength) and also carbonyl index. The results obtained revealed that Fe-GA efficiency in enhancing oxidation rate of polymer upon UV exposure is remarkably much more than of GA. In contrast, Br-GA is responsible for initiating photo-oxidation of the polymer and has negligible effects on the rate of degradation. Based on the results obtained, it was proposed that the photo-activity of GA in the polymer arises from the C=C bond present in the side group attached to aromatic lacton rings of additive molecule, probably through its reaction with singlet oxygen and subsequent generation of hydroperoxide. This mechanism in combination with catalytic effect of iron (III) accounted for the higher effect of Fe-GA in accelerating photo-oxidation rate of the polymer.