Cuproptosis, a recently identified form of regulated cell death, is triggered by intracellular copper accumulation, leading to subsequent protein lipoylation or pyruvate uptake. The ubiquitin-proteasome system plays a key role in copper-induced cell death. This study aims to identify the deubiquitinase-mediated regulation of cuproptosis in hepatocellular carcinoma. UCHL3 was identified as a key regulator of cuproptosis via the deubiquitinase siRNA library screening. UCHL3 knockdown inhibited elesclomol-CuCl-induced cuproptosis, whereas its overexpression enhanced cuproptosis. Correspondingly, UCHL3 inhibition suppressed cuproptosis, while activation of UCHL3 promoted it. Ubiquitinome profiling revealed that UCHL3 modulates the pyruvate biosynthetic process, cellular response to metal ions, and hypoxia. Its downstream effects were enriched in glycolysis and the HIF-1 signaling pathway. PKM2 emerged as a key node within the UCHL3 substrate network. Wild-type UCHL3, instead of its active site mutant (C95A), deubiquitinated and stabilized PKM2. The PKM2 K206R mutation prevented PKM2 ubiquitination. UCHL3 directly interacted with PKM2. Pharmacological or genetic inhibition of PKM2 impaired cuproptosis in hepatocellular carcinoma. Conversely, overexpression of wild-type PKM2 or activation of PKM2 promoted cuproptosis. Both UCHL3 and PKM2 promoted pyruvate biosynthesis. Moreover, pyruvate directly enhanced cuproptosis induced by elesclomol-CuCl in HCC. In vivo, UCHL3 facilitated cuproptosis induced by elesclomol-CuCl. In conclusion, UCHL3 enhances cuproptosis by deubiquitinating and stabilizing PKM2 at the K206 site in hepatocellular carcinoma, presenting a novel therapeutic avenue for treatment.