Uncatalyzed liquid-phase oxidation of cyclohexene was performed under mild reaction conditions of 40 to 100 °C and 10 to 20 bar O2 to obtain comprehensive knowledge on its autoxidation kinetics and reaction mechanisms. An Arrhenius analysis clearly identified a transition of the dominating reaction step within the investigated temperature range. The formation of 2-cyclohexene-1-hydroperoxide was found to be the dominating reaction of cyclohexene oxidation below 80 °C with an apparent activation energy of 40 kJ mol−1, whereas the thermal hydroperoxide decomposition prevails at temperatures above 80 °C and an apparent activation energy of 95 kJ mol-1 was obtained. Cyclohexenyl, cyclohexenyl alkoxyl and cyclohexenyl peroxyl radicals were identified playing a decisive role in cyclohexene oxidation in the absence of any catalyst. High pressures were found to inhibit cyclohexene conversion, which was attributed to a larger radical recombination rate. The decomposition of 2-cyclohexene-1-hydroperoxide was identified to proceed via a unimolecular homolytic decomposition into the cyclohexenyl and superoxide radicals. The addition of 2-cyclohexene-1-hydroperoxide accelerates the rate of cyclohexene oxidation, while it is suppressed in the presence of the final products 2-cyclohexene-1-ol and 2-cyclohexene-1-one. Cyclohexane-1,2-diol was shown to be a product of the allylic pathway of cyclohexene oxidation, while cyclohexene oxide is exclusively formed by epoxidation.