In this study, we used murine chondrocytes as an in vitro model and mice exhibiting destabilization of the medial meniscus (DMM) as an in vivo model to investigate the mechanisms through which S-allyl cysteine (SAC) alleviates osteoarthritis (OA). SAC significantly reduced apoptosis and senescence and maintained homeostasis of extracellular matrix (ECM) metabolism in tert-butyl hydroperoxide (TBHP)-treated chondrocytes. Molecular docking analysis showed a –CDOCKER interaction energy value of 203.76 kcal/mol for interactions between SAC and nuclear factor erythroid 2-related factor 2 (Nrf2). SAC increased the nuclear translocation of Nrf2 and activated the Nrf2/HO1 signaling pathway in TBHP-treated chondrocytes. Furthermore, Nrf2 knockdown abrogated the antiapoptotic, antisenescence, and ECM regulatory effects of SAC in TBHP-treated chondrocytes. SAC treatment also significantly reduced cartilage ossification and erosion, joint-space narrowing, synovial thickening and hypercellularity in DMM model mice. Collectively, these findings show that SAC ameliorates OA pathology in TBHP-treated chondrocytes and DMM model mice by activating the Nrf2/HO1 signaling pathway.