Anemia is a frequent complication of ulcerative colitis, and is frequently caused by iron deficiency. Oral iron supplementation displays high rates of gastrointestinal adverse effects. However, the formulation of sucrosomial iron (SI) has shown higher tolerability. We performed a prospective study to compare the effectiveness and tolerability of oral SI and intravenous ferric carboxy-maltose (FCM) in patients with ulcerative colitis in remission and mild-to-moderate anemia. Patients were randomized 1:1 to receive 60 mg/day for 8 weeks and then 30 mg/day for 4 weeks of oral SI or intravenous 1000 mg of FCM at baseline. Hemoglobin and serum levels of iron and ferritin were assessed after 4, 8, and 12 weeks from baseline. Hemoglobin and serum iron increased in both groups after 4 weeks of therapy, and remained stable during follow up, without significant treatment or treatment-by-time interactions ( = 0.25 and = 0.46 for hemoglobin, respectively; = 0.25 and = 0.26 for iron, respectively). Serum ferritin did not increase over time during SI supplementation, while it increased in patients treated with FCM (treatment effect, = 0.0004; treatment-by-time interaction effect, = 0.0002). Overall, this study showed that SI and FCM displayed similar effectiveness and tolerability for treatment of mild-to-moderate anemia in patients with ulcerative colitis under remission.