Infertility is somewhat more prevalent in men who are obese. They are also reported to have low sperm concentration, higher fraction of spermatozoa that look morphologically abnormal, higher DNA fragmentation index and evidence of oxidative stress. The precise cause for this remains uncertain. Leptin levels in serum and percentage body fat correlate positively, and obese men therefore usually have elevated serum leptin levels. Although leptin is important for normal reproductive function, but when present in excess, leptin could seriously affect reproductive function in men. Reports on the findings of sperm parameters in obese men, particularly those who are subfertile or infertile, seem to be similar to those reported from studies on normal-weight rats treated with leptin. Collectively, the observations reported in human and experimental animal studies point to leptin as a possible link between infertility and obesity. Herein, we review some findings on sperm function in obese subfertile or infertile men and those from animal studies following leptin treatment, and discuss the possible link between leptin and reproductive dysfunction in obese men. The large amounts of leptin secreted by the adipose tissue and its higher circulating levels could indeed be responsible for the higher prevalence of infertility in obese men.