Anemia is encountered in patients with nonvalvular atrial fibrillation (NVAF) on oral anticoagulants (OACs) but the prognostic impact was not well scrutinized in real-world settings. We conducted a historical multicenter registry of patients with NVAF taking OACs at 71 centers in Japan. Those with mechanical heart valves or a history of pulmonary thrombosis or deep venous thrombosis were excluded. Anemic patients were divided into three groups of hemoglobin (Hb) level: moderate/severe (Hb < 11.0 g/dL), mild (men: Hb of 11.0-12.9 g/dL; women: Hb of 11.0-11.9 g/dL), and no anemia. The endpoints included major bleeding, hemorrhagic stroke, ischemic events, ischemic stroke, and all-cause mortality. Among 7558 consecutive patients (mean age, 73 years; men 67%) registered in February 2013 and followed until February 2017, 2100 (28%) patients had anemia. The anemic patients were older (moderate/severe: 79 years; mild: 77 years; no anemia: 71 years, p < .001), and HAS-BLED score was significantly higher in the anemic patients (p < .001). The cumulative incidences at 4 years of major bleeding in moderate/severe, mild, and no anemia group, were 14.9%, 10.7%, and 6.4%, respectively. The adjusted hazard ratios (HRs) (95% confidential intervals (CIs)) of major bleeding of moderate/severe and mild anemia group were 1.96 (1.49-2.58) and 1.48 (1.17-1.87) compared to no anemia group. The adjusted HRs (95% CIs) for ischemic events were 0.63 (0.39-0.99) and 1.03 (0.76-1.39). The severity of anemia in the patients with NVAF on OACs was associated with major bleeding.