This paper concerns the experimental analysis of the effect of irradiance on the photooxidation of low-density polyethylene (LDPE) stabilized with different HALS. Infrared analysis in transmission mode was used to monitor the extent of oxidation provoked by the exposure of thin samples (100 µm thick) in a SEPAP MHE unit (Atlas/Ametek) at two different irradiances (90 W.m − 2 and 300 W.m − 2 between 300 and 420 nm). The temperature of the samples was maintained constant in order to focus on the impact of irradiance on the kinetics, without interfering with the temperature. The intended goal was to characterize the effect of the irradiance in accelerated testing and the consequences on the lifetime prediction. Previous results obtained in the case of unstabilized LDPE samples showed that no acceleration was obtained when increasing the irradiance from 90 W. m − 2 and 300 W.m − 2 while keeping the temperature constant. In the case of the stabilized samples, the results presented in the present article show that the rates of photo oxidation tended to increase when increasing the irradiance. However, the ratio of these rates never reaches the ratio of the irradiances, and these ratios depends on the stability of the samples.