Male obesity is associated with reduced sperm motility and morphology and increased sperm DNA damage and oxidative stress; however, the reversibility of these phenotypes has never been studied. Therefore, the aim of this study was to assess the reversibility of obesity and its associated sperm physiology and function in mice in response to weight loss through diet and exercise. C57BL6 male mice (n = 40) were fed either a control diet (CD; 6% fat) or a high-fat diet (HFD; 21% fat) for 10 wk before allocation to either diet and/or swimming exercise interventions for 8 wk. Diet alone reduced adiposity (1.6-fold) and serum cholesterol levels (1.7-fold, P < 0.05), while exercise alone did not alter these, but exercise plus diet also improved glucose tolerance (1.3-fold, P < 0.05). Diet and/or exercise improved sperm motility (1.2-fold) and morphology (1.1-fold, P < 0.05), and reduced sperm DNA damage (1.5-fold), reactive oxygen species (1.1-fold), and mitochondrial membrane potential (1.2-fold, P < 0.05) and increased sperm binding (1.4-fold) (P < 0.05). Sperm parameters were highly correlated with measures of glycemia, insulin action, and serum cholesterol (all P < 0.05) regardless of adiposity or intervention, suggesting a link between systemic metabolic status and sperm function. This is the first study to show that the abnormal sperm physiology resulting from obesity can be reversed through diet and exercise, even in the presence of ongoing obesity, suggesting that diet and lifestyle interventions could be a combined approach to target subfertility in overweight and obese men.