ABSTRACT Background and Objective: There have been concerns over possible association between mercury and neurodevelopmental outcomes in infants. In this study we aimed to determine whether blood levels of mercury are above safe values in Iranian infants or not. Materials and Methods: A total of 85 infants (0, 2, 4 and 6 months old) were enrolled in this study. All of them received vaccines according to Iranian immunization schedules. We measured total mercury in all blood samples by cold vapor atomic absorption. Results: The mean concentration of blood mercury in our subjects were as follows: newborns as 33.95 ± 11.86 nmol/l (with a range of 23.93-52.84), 2 months as 32.94 ± 11.76 nmol/l (with a range of 23.92-52.84), 4 months as 30.44 ± 10.44 nmol/l (with a range of 23.92-50.85) and 6 months as 37.93 ± 12.97 nmol/l (with a range of 21.43-52.34). There was not any significant difference for the mean concentration of blood mercury in those age groups. The lowest level of blood mercury detected was 21.43 nmol/l and the highest level was 52.84 nmol/l. Conclusion: The finding of this study showed that approximately 33% of the infants had blood mercury levels above the U.S. Environmental Protection Agency recommended reference dose of 5.8 μg/l (29 nmol/l). Therefore, it is needed to reduce exposure of infants to mercury from all sources including thimerosal containing vaccines (TCVs) in Iran.