Background and Purpose: Obesity and Type 2 Diabetes are major causes of morbidity-mortality characterized by mitochondrial dysfunction and oxidative-nitrosative stress. Despite intensive research, the events that cause the onset and progression of these diseases are not completely understood. Herein, we investigated if dysregulation of mitochondrial dynamics and biogenesis is involved in an animal model of obesity and diabetes. Experimental Approach: Mitochondrial dynamics and biogenesis were evaluated in epididymal white adipose tissue and adipocytes from ob/ob mice, an animal model of obesity and diabetes, pharmacological treatment with mdvi-1, a selective inhibitor of Drp1 and leptin. Key Results: A decrease of Mfn2 and OPA-1 protein expression and an increase in Drp1- protein levels were observed with enhanced and sustained mitochondrial fragmentation in ob/ob mice compared to wt C57BL/6 animals. The content of mitochondrial DNA and mRNA expression of PGC-1α, both parameters of mitochondrial biogenesis, were reduced in ob/ob mice. The treatment with leptin or mdvi-1 (Drp1 inhibitor) significantly increased abnormal biogenesis, improved fusion-to-fission balance and attenuated mitochondrial dysfunction, and adipogenesis, thus inducing white-to-beige adipocyte transdifferentiation. Measurements of glucose and lipid oxidation in adipocytes revealed that both leptin and mdvi-1 increase substrates oxidation while in vivo determination of blood glucose showed decreased blood glucose concentration by 50 % in ob/ob mice, almost to the wt level. Conclusion and Implications: In light of these results, pharmacological targeting of Drp1 may be a potential novel therapeutic tool for obesity and diabetes.