Although azacitidine is the first‐line drug for higher‐risk myelodysplastic syndrome (MDS) patients, its efficacy for lower‐risk MDS remains unestablished. Therefore, we conducted a prospective study to examine the efficacy and safety of a 5‐day regimen of azacitidine (AZA‐5) for lower‐risk MDS. The primary endpoint was hematological improvement (HI) after 4 courses of therapy. A total of 51 patients with lower‐risk MDS based on the French‐American‐British (FAB) classification (44 patients with refractory anemia RA and 7 patients with refractory anemia with ringed sideroblasts RARS) were enrolled from 6 centers in Japan. The median age was 75 years (range: 51‐88). These patients received AZA‐5 (75 mg/m2; once daily for 5 sequential days). The median number of AZA‐5 courses was 8 (range: 1‐57), and 45 patients (88.2%) received more than 4 courses. HI and transfusion independency were seen in 24 patients (47.1%) and 11 patients (39.2%), respectively. A total of 11 patients (21.6%) achieved complete remission or marrow remission. WT1 mRNA levels were not significantly correlated with therapy response. Grade 3 or 4 neutropenia and thrombocytopenia occurred in 26 (51.0%) and 11 (21.5%) patients, respectively. Nonhematological grade 3 or 4 adverse events were observed in 9 patients (17.6%). Together, these results indicate that AZA‐5 is feasible and effective for lower‐risk MDS patients as well as for higher‐risk MDS patients. Five‐day regimen of azacitidine for lower‐risk MDS.