Background: Iron deficiency anaemia remains one of the most common nutritional disorders among pregnant women worldwide. In Kenya, anaemia during pregnancy continues to pose a significant public health challenge despite the routine provision of iron and folic acid supplementation (IFAS) through antenatal care (ANC) services. However, compliance with IFAS remains low, particularly in the Rift Valley region.

Objective: This study aimed to determine the predictors of IFAS compliance during pregnancy among mothers with infants aged 0-11months old attending Maternal and Child Healthcare (MCH) services at Kamwosor Sub-County hospital, Elgeyo Marakwet County.

Methods: A facility-based retrospective cross-sectional mixed-methods study was conducted among 127 randomly selected mothers. Quantitative data were collected using a researcher-administered electronic questionnaire, while qualitative data were obtained through Focus Group Discussions with mothers and Key Informant Interviews with health workers. Quantitative data were analyzed using descriptive statistics, bivariate analysis and multivariable logistic regression, while qualitative data were analyzed thematically.

Results: Overall, 33.3% of mothers were compliant with IFAS, defined as taking supplements for at least 90 days during the most recent pregnancy. The predictors of IFAS compliance included early ANC initiation during the first trimester (AOR = 2.576; 95% CI: 2.521–2.891; p < 0.01), attending more than four ANC visits (AOR = 1.911; 95% CI: 1.721–2.121; p < 0.01), receiving interpersonal counselling (AOR = 3.949; 95% CI: 3.871–4.124; p < 0.01), and having a positive attitude toward IFAS (AOR = 1.932; 95% CI: 1.904–2.311; p < 0.01). Frequent IFAS stock outs, reliance on herbal remedies, negative attitudes and beliefs and inadequate counselling were the major barriers to IFAS compliance.