In the context of antenatal care, adherence to routine medications is vital for preventing adverse pregnancy outcomes and ensuring maternal and fetal health. Non-adherence can lead to a range of complications, including maternal anemia, preterm birth, low birth weight, and congenital abnormalities. This study aimed to assess adherence to routine antenatal medications and its determinant among pregnant women in selected primary health centers in Ogbomoso North, Oyo state. A descriptive research design was used in this study and convenience sampling technique was used to recruit 136 respondents. A self-structured questionnaire of reliability index 0.768 was used as instrument of data collection. The responses were analysed with descriptive statistic (frequency and table) using SPSS Version 23 and the hypothesis stated was tested using inferential statistics (chi square). The results showed that the study concluded that majority of the respondents 93(68.4%) have good perception and 43(31.6%) have poor perception towards the adherence of routine antenatal medications. Majority of the respondents 76(55.9%) has low level of adherence and 60(44.1%) has high level of adherence to routine antenatal medications. The determinants of adherence to routine antenatal medications are accessibility of routine antenatal medications 113(83.1%), experience in previous pregnancies 97(71.3%), and support from family or partner 84(61.8%). There is significant relationship between sociodemographic characteristics and adherence to routine antenatal medications among pregnant women in selected primary health centers (religion (0.000), level of education (0.014), ethnicity (0.000), marital status (0.001), employment status (0.006), household income (0.038) and number of pregnancies (0.000)]. Also, there is no significant relationship between determinants (accessibility and availability) and adherence to routine antenatal medications among pregnant women in selected primary health. In conclusion, there should be regular antenatal educations on the routine antenatal medications during the antenatal visits.