OBJECTIVES:  The use antiretroviral therapy (ART) has impacted positively on the rate of transmission of Human Immuno-Deficiency Virus (HIV) from mother to child by reducing the risk of infection to less than 2% during pregnancy but without intervention the risk of transmission ranges from 20% to 45%. However, adherence level >95% is crucial to accomplishing the aforementioned benefit of reduced risk of transmission of HIV. This research aims to examine the level of adherence of HIV positive pregnant women to the new streamlined ART regimen of Tenofovir based fixed dose combination in Nigeria for prevention of HIV from mother to child and the risk factors for nonadherence. METHODS:  This was a cross-sectional survey, where the adherence of 160 HIV positive pregnant women taking fixed dose Tenofovir based regimen was evaluated using a self-administered study- specific 16 element structured questionnaire. The number of prescribed doses of medication missed and the mean scores of the patient’s adherence to the medication schedule was used to calculate the self- reported adherence. RESULTS: Majority of the participants (96.25%) were between the age group of 15-44 years. The mean self-reported adherence with respect to taking the fixed dose combination of Tenofovir once in a day was 89.4%. Depression, 46 (48.8%) ranked as the number one risk factor for non-adherence among the HIV positive pregnant women and the second major ranked risk factor for non-adherence to medication is stigma; 41(25.6%) reported that the main reason why they missed or delayed taking their medication was because they were afraid that others may know that they are taking ARV drugs. CONCLUSIONS:  The study reported sub-optimal medication adherence level of 89.4% by comparison to the acceptable adherence level > 95% required to accomplish viral load suppression that will substantially reduce the risk of transmission of HIV from mother to the child during pregnancy.