Background: The optimal on-scene time after the return of spontaneous circulation (ROSC) following out-of-hospital cardiac arrest (OHCA) has not been established. This study aimed to investigate the relationship between the on-scene time after ROSC and neurological outcomes. Methods: We analyzed data recorded in the SOS-KANTO 2017 registry between September 2019 and March 2021. Patients with OHCA who achieved ROSC on the scene were included and categorized into three groups based on on-scene time after ROSC (0-<6 min, 6-<10 min, and ≥10 min). Comparisons were performed using multiple propensity score analysis. The primary outcome was favorable neurological status at one month, defined as cerebral performance categories 1 and 2. Results: In total, 331 patients were included. Favorable neurological outcomes at one month were observed in 29.1% (32/123) of patients in the 0-<6 min group, 37.2% (35/104) in the 6-<10 min group, and 36.3% (29/104) in the ≥10 min group. There was no significant association between shorter on-scene times (0-<6 min) and favorable neurological outcomes at one month compared to the other groups (adjusted odds ratio [AOR], 0.97; 95% confidence interval [CI], 0.39-2.41 for 6-<10 min; AOR, 0.90; 95% CI, 0.30-2.70 for ≥10 min). Conclusion: Differences in on-scene time after ROSC were not significantly associated with favorable neurological outcomes at one month. Future research should focus on identifying factors that may influence outcomes, and on exploring strategies to enhance care in the Japanese EMS context.