BACKGROUND The aim of this study was to investigate the effects of sleep duration and bedtime on sperm health, and the possible mechanism involved. MATERIAL AND METHODS We randomly divided 981 healthy Chinese men into groups according to research-set bedtimes (A=8-10 PM, B=after 10 PM, and C=after midnight) and sleep durations: group 1=<6.0 h (short), group 2=7.0-8.0 h (average), and group 3=>9.0 h (long). Sperm morphology, count, survival, and motility were examined according to sleep patterns. Antisperm antibody (ASA) production in semen was determined. RESULTS Sperm counts and their survival rates were lower in the short sleepers as compared to others within each group (all P<0.01). The lower counts and survival rates were observed in different bedtimes, with significant differences found between measurements of C1 vs. A1 and C2 vs. A2 or B2 (all P<0.05 or 0.01). Semen motility was lower in the short sleepers as compared to the average and long sleepers (all P<0.01). There were differences in the bedtime-related results between measurements of C1 vs. A1 or B1 (P<0.05 or 0.01). Additionally, the population proportion for the ASA-positive participates and incidence of the ASA-expressed population obviously increased in the short sleepers as compared to others within each group (all P<0.05). CONCLUSIONS Short and long sleep durations and late bedtime were associated with impaired sperm health in the study cohort, partly through increasing ASA production in the semen.