The circadian timing system regulates key aspects of mammalian physiology. Here, we analysed the effect of the endogenous antioxidant paraoxonase 1 (PON1), an HDL-associated lipo-lactonase that hydrolyses lipid peroxides and attenuates atherogenesis, on circadian gene expression in C57BL/6J and PON1KO mice fed a normal chow diet (ND) or a high-fat diet (HFD). Expression levels of core-clock transcripts Nr1d1, Per2, Cry2 and Bmal1 were altered in skeletal muscle in PON1-deficient mice in response to HFD. These findings were supported by circadian bioluminescence reporter assessments in mouse C2C12 and human primary myotubes, synchronized in vitro, where administration of PON1 or pomegranate juice modulated circadian period length.