Vertical transmission of hepatitis B virus (HBV), especially in Asia, is a key target in the global elimination of HBV. This study assessed the effects of tenofovir disoproxil fumarate (TDF) in pregnant women for mother-to-infant transmission of HBV. A total of 122 pregnant women at our hospital met the inclusion criteria for high HBV DNA viral loads. They were randomly divided into TDF-treatment (n=70) and placebo (n=52) groups. Maternal liver function and serum HBV DNA load were tested before and after treatment. Clinical and laboratory data of infants were assayed at delivery and 7-months post-partum visit and compared between the two groups. There was no difference in clinical characteristics of participants between the two groups. There were no significant differences in liver function markers, including alanine aminotransferase, total bilirubin, blood creatinine, and blood urea nitrogen levels before and after TDF treatment. The serum HBV DNA viral load of the TDF-treated group became significantly lower than those of the control group and their own pre-medication levels. Infants showed no significant difference in body growth, including weight, height, head size, and five-min Apgar score. At 7 months after birth, 94.29% of infants in the TDF group and 86.54% of control-group infants had protective HBsAb levels ≥ 10 mIU/ml (p>0.05). The HBV infection rate of infants in the TDF-treated group was lower than that in the non-treated group. In high-HBV-DNA-load pregnant women, TDF administered from 28 weeks gestational age to delivery was associated with a lower risk of mother-to-infant transmission of HBV.