Background: iron deficiency anemia among mothers is a serious public health issue.Studies found a link between adverse events and iron supplementation compliance during pregnancy. Objectives: to assess the compliance to iron supplementation among pregnant women with iron deficiency anemia in Riyadh, Saudi Arabia, and its determinants and barriers. Methods: a cross-sectional study was done in Riyadh, Saudi Arabia on pregnant women with iron deficiency anemia who attended primary health care centers (PHCCs) in Riyadh, Saudi Arabia. An online questionnaire wasused to collect data about womens demographics, obstetric and gynecological history, prescribed iron supplements, womens awareness regarding iron deficiency anemia, compliance with iron/folate supplementation, and reasons for non-compliance. Results: 74.8% of females sometimes forget to take iron supplements, 54.1% reduced or stopped taking iron supplements without telling their doctor because they felt worse when taking them, and 63.5% sometimes forget to bring or take iron supplements when they leave home. The prevalence of low, medium and high compliance with iron supplement intake was 74.2%, 15.1%, and 10.7%, respectively, among the participants.Side effects (43.4%) and forgetting (32.1%) were the most common reasons for noncompliance. High compliance was significantly higher among participants over the age of 30, with a university education or higher, in the trimester, who had ≥ 5 antenatal visits, and who preferred iron supplements in tablet form. Conclusion: The low observed compliance among studied females emphasizes the importance of increasing communication for behavior change and counseling before or during antenatal care to improve adherence.