Sulforaphane (SFN) prevents diabetic nephropathy (DN) in type 2 diabetes (T2D) by up-regulating nuclear factor (erythroid-derived 2)-like 2 (Nrf2). AMP-activated protein kinase (AMPK) can attenuate the pathogenesis of DN by improving renal lipotoxicity along with the activation of Nrf2-mediated antioxidative signaling. Therefore, we investigated whether AMPKα2, the central subunit of AMPK in energy metabolism, is required for SFN protection against DN in T2D, and whether potential cross-talk occurs between AMPKα2 and Nrf2. AMPKα2 knockout (Ampkα2−/−) mice and wildtype (WT) mice were fed a high-fat diet (HFD) or a normal diet (ND) to induce insulin resistance, followed by streptozotocin (STZ) injection to induce hyperglycemia, as a T2D model. Both T2D and control mice were treated with SFN or vehicle for 3 months. At the end of the 3-month treatment, all mice were maintained only on HFD or ND for an additional 3 months without SFN treatment. Mice were killed at sixth month after T2D onset. Twenty-four-hour urine albumin at third and sixth months was significantly increased as renal dysfunction, along with significant renal pathological changes and biochemical changes including renal hypertrophy, oxidative damage, inflammation, and fibrosis in WT T2D mice, which were prevented by SFN in certain contexts, but not in Ampkα2−/− T2D mice. SFN prevention of T2D-induced renal lipotoxicity was associated with AMPK-mediated activation of lipid metabolism and Nrf2-dependent antioxidative function in WT mice, but not in SFN-treated Ampkα2−/− mice. Therefore, SFN prevention of DN is AMPKα2-mediated activation of probably both lipid metabolism and Nrf2 via AMPK/AKT/glycogen synthase kinase (GSK)-3β/Src family tyrosine kinase (Fyn) pathways.