AIM: This study was conducted to determine whether weekly antenatal oral iron and folate supplementation is an effective alternative to a daily regimen in non-anemic pregnant women to prevent anemia and iron deficiency during the third trimester. METHODS: From December 2014 to April 2015, non-anemic pregnant women (n = 292) who presented to the Academic Obstetric Unit, Teaching Hospital Mahamodera Galle, Sri Lanka, at 14-22 weeks gestation and who had been treated with mebendazole 100 mg twice daily for three days were randomly allocated to receive 120 mg elemental iron, 3 mg folic acid and 100 mg vitamin C weekly (n = 149) or 60 mg elemental iron, 1 mg folic acid and 100 mg vitamin C daily (n = 143). Side effects were assessed at four weekly intervals and hemoglobin concentration (Hb), hematocrit and serum ferritin (SF) were measured at 32-36 weeks gestation. RESULTS: Only 106 participants in each group completed the study. There were no significant differences between the groups in mean duration of supplementation; presupplementation and post-supplementation mean Hb, hematocrit or SF levels; risk of developing anemia, ID or high Hb levels by an intension to treat analysis; and in those who completed the trial. Significantly greater side effects occurred in the daily compared to the weekly supplementation group. CONCLUSION: In non-anemic pregnant women, a weekly regimen is an effective alternative to a daily regimen for antenatal oral iron and folate supplementation for preventing anemia and iron deficiency during the third trimester.