The nephrotoxicity of cisplatin (cis-DDP) limits its general clinical applications. Lentinan (LNT), a dextran extracted from the mushroom Lentinula edodes, has been shown to have multiple pharmacological activities. The primary objective of the current study was to determine whether and how LNT alleviates cis-DDP- induced cytotoxicity in HK-2 cells and nephrotoxicity in mice. LNT did not interfere with cisplatin's anti-tumour efficacy in vitro and functioned cooperatively with cis-DDP to inhibit activity in HeLa and A549 tumour cells. LNT alleviated the cis-DDP-induced decrease in HK-2 cell viability, caspase-3 activation and cleavage of the DNA repair enzyme PARP, decreased HK-2 cell apoptosis and inhibited reactive oxygen species (ROS) accumulation in HK-2 cells. The inhibitor of ROS (N-acetyl-L-cysteine, NAC) could decreased the apoptosis of HK-2 cell. In addition, LNT significantly prevented cis-DDP-induced kidney injury in vivo. LNT itself could not eliminate ROS levels in vitro. Further studies demonstrated that LNT induced NF-E2 p45-related factor 2 (Nrf2) protein and mRNA expression in a time- and dose-dependent manner. LNT promoted Nrf2 translocation to the nucleus and binding to the antioxidant-response element (ARE) sequence and induced the transcription and translation of heme oxygenase 1 (HO-1), aldo-keto reductases 1C1 and 1C2 (AKR1C), and NADP(H):quinone oxidoreductase 1 (NQO1). Finally, we used hNrf2 siRNA and an Nrf2 agonist (tBHQ) to inhibit or enhance Nrf2 expression. The results demonstrated that the LNT-mediated alleviation of cis-DDP-induced nephrotoxicity was achieved by preventing the accumulation of ROS in a manner that depended on the activation of the Nrf2-ARE signalling pathway.