AIMS: To assess the impact of baseline characteristics on the efficacy and safety of oral semaglutide in Japanese patients with type 2 diabetes. MATERIALS AND METHODS: In PIONEER 9 and 10, Japanese patients were randomized to once-daily oral semaglutide (3, 7, or 14 mg) or a comparator (placebo or once-daily subcutaneous liraglutide 0.9 mg in PIONEER 9; once-weekly subcutaneous dulaglutide 0.75 mg in PIONEER 10) for 52 weeks, with 5 weeks of follow up. An exploratory analysis grouped patients in each trial according to baseline glycated hemoglobin (HbA1c ; ≤8.0, >8.0-≤9.0, or >9.0%), body mass index (<25, ≥25-<30, or ≥30 kg/m2 ), and, for PIONEER 10 only, by background medication (sulfonylurea, glinide, thiazolidinedione, α-glucosidase inhibitor, sodium-glucose cotransporter-2 inhibitor). Efficacy (changes from baseline to week 26 in HbA1c and body weight) and safety were assessed. RESULTS: 701 patients were included (PIONEER 9: N = 243; PIONEER 10: N = 458). In both trials, HbA1c reductions increased as baseline HbA1c increased; there were no other apparent patterns between the variables investigated and HbA1c or body weight changes. There was one statistically significant subgroup interaction between baseline HbA1c and estimated treatment differences in body weight change for oral semaglutide 14 mg versus placebo in PIONEER 9 (P = 0.0286). Baseline HbA1c , baseline body mass index and background medication did not appear to affect the proportions of patients reporting adverse events. CONCLUSIONS: Oral semaglutide is effective across a range of baseline subgroups of Japanese patients with type 2 diabetes, with no unexpected safety findings.