Introduction The INPULSIS-ON trial demonstrated that nintedanib reduced decline in forced vital capacity (FVC) and low pulmonary function (%FVC < 50%) of patients with idiopathic pulmonary fibrosis (IPF). However, there is no sufficient evidence in real world. Objectives Reveal the utility and adverse events of nintedanib for severe IPF patients. Methods This was a single-center retrospective study. Patients who met the eligibility criteria of the INPULSIS trial (%FVC ≥ 50%; %DLCO [diffusing capacity of the lung carbon monoxide % predicted] ≥ 30%) were classified as Mild to Moderate Group (n = 34); patients who did not meet the criteria were classified as Severe Group (n=17). Results The body mass index (24.7 ± 3.4 vs 22.4 ± 3.6 kg/m2; P = 0.021) were significantly low in Severe Group. Main adverse events (diarrhea, nausea, liver disorder, and acute exacerbation) tended to be more in Severe Group than in Mild to Moderate Group; however, the difference was not significant (P = 0.76, 0.14, 0.18, and 0.67, respectively). The continuation rates over 12 months tended to be higher in Mild to Moderate Group than in Severe Group (77% vs 44%; P = 0.027). Log-rank test revealed that the prognosis was significantly better in Mild to Moderate Group than in Severe Group (P = 0.014). In the Severe Group, patients who were able to continue nintedanib for more than 3 months had significantly better prognosis compared to those who could not (P = 0.007). Conclusion The benefit from nintedanib was reduced in patients in Severe Group when compared to those in Mild to Moderate Group; however, the prognosis is expected to improve with control of side effects and long-term administration. It is more important to control the side effects in Severe Group.