Diabetes-induced testicular cell death is predominantly due to oxidative stress. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is an important transcription factor in controlling the anti-oxidative system and is inducible by sulforaphane (SFN). To test whether SFN prevents diabetes-induced testicular cell death, an insulin-defective stage of type 2 diabetes (IDS-T2DM) was induced in mice. This was accomplished by feeding them a high-fat diet (HFD) for 3 months to induce insulin resistance, and then giving one intraperitoneal injection of streptozotocin to induce hyperglycemia while age-matched control mice were fed a normal diet (ND). IDS-T2DM and ND-fed control mice were then further subdivided into those with or without 4-month SFN treatment. IDS-T2DM induced significant increases in testicular cell death presumably through receptor and mitochondrial pathways, shown by increased ratio of Bax/Bcl2 expression and cleavage of caspase-3 and caspase-8 without significant change of endoplasmic reticulum stress. Diabetes also significantly increased testicular oxidative damage and inflammation. All these diabetic effects were significantly prevented by SFN treatment with up-regulated Nrf2 expression. These results suggest that IDS-T2DM induces testicular cell death presumably through caspase-8 activation and mitochondria-mediated cell death pathways, and also by significantly down-regulating testicular Nrf2 expression and function. SFN up-regulates testicular Nrf2 expression, and its target antioxidant expression, which was associated with significant protection of the testis from IDS-T2DM-induced germ cell death.