Abstract Auto-oxidation of polyethylene (PE) is of a common occurrence and could be triggered by several physical and chemical factors. In this study, for the first time, we report a comprehensive theoretical account on the initial oxidation of crystalline PE at low temperatures prior to its melting. We map out potential energy surfaces for large number of reactions, most notably, initial abstraction by O2 molecules, formation of peroxy- and hydroperoxyl adducts, unimolecular eliminations of HO2 and H2O as well as C C bond fissions. Rate constants have been estimated for all considered reactions over the temperature range of 300–800 K. We have discussed noticeable similarities between the oxidation of PE and that of gas-phase alkanes. Results presented herein provide new insights into the solid-state oxidation of PE and germane crystalline polyolefins/paraffins and pure carbon–hydrogen-type polymers.