Background/aim: It has been reported from in vivo exposed experimental animals that paternal lead exposure reduces birth rate; however, there is limited evidence to suggest a decrease in the proportion of male births. This study investigated the role of paternal exposure to lower lead acetate doses on early embryonic development (implantation) and the sex ratio of their offspring. Materials and methods: In total 180 Swiss Webster mice were used (60 male and 120 female). The males were divided into 3 groups: G1 (untreated group), G2 (treated daily with 50 μg/kg BW lead acetate), and G3 (treated daily with 100 μg/kg BW lead acetate). The implantation success rate, pregnancy outcome, and sex ratio were measured. Results: The results showed a highly significant reduction in both the percentage of implantation rate and the number of offspring in the G3 mice, but there was no signification difference for the G2 mice. There was a slight insignificant reduction in the number of newborn males compared with females for both G2 and G3 mice. Conclusion: The findings of this study suggest lead exposure in experimental animals reduces implantation rate with paternal BLL of 28 μg/dL and the sex ratio for offspring showed a slight insignificant reduction with both paternal BLLs of 23.5 μg/dL and 28 μg/dL.