About 32 million pregnant women are at the risk of malaria infection yearly in malaria-endemic sub-Saharan Africa. To mitigate the risks associated with malaria in pregnancy, the WHO recommends ≥3 doses of intermittent preventive treatment in pregnancy (IPTp) with sulphadoxine-pyrimethamine (SP), covering from the second trimester of pregnancy until delivery. This cross-sectional study assessed the uptake and extent of adherence with IPTp-SP among pregnant women in Osun State, Nigeria, from October 2020 to March 2021. Assessment of the uptake was done by extracting information from the validated case report forms. Venous blood samples were obtained to assess the levels of sulphadoxine in plasma through HPLC-UV. In total, 49.24%, 38.17% and 12.58% of the study participants obtained 1, 2 and ≥3 doses of IPTp-SP, respectively. In assessing the extent of adherence, 46.67% obtained their last dose within 28 d before sample collection. Uptake of IPTp-SP is not associated with gravidity (p=0.603), but is weakly associated with the age of the study participants (p=0.04). The median (IQR) plasma sulphadoxine concentration was 10.6248 (2.8124-27.1242) ug/mL. Utilisation of the intervention is still very low and adherence appears to be inadequate among the study population, suggesting that more advocacy on the IPTp-SP strategy and the implementation of directly observed therapy is necessary.