INTRODUCTION: Out-of-hospital cardiac arrest (OHCA) remains an important health care issue. Considering the importance of such a time course after cardiac arrest, detailed evaluation of the prehospital time (i.e., time from EMS contact to a patient to hospital arrival) is essential to improve the mortality and neurologic outcome of OHCA. In this study, we aimed to evaluate the impact of prehospital time on neurological outcomes in patients with OHCA. METHODS: This retrospective observational study included adult non-traumatic OHCA patients who were transported to 2 emergency centers in Tokyo from January 2015 to December 2020. The following data were obtained retrospectively from medical records. RESULTS: Of the 3120 OHCA patients who were transported during the study period, 2215 patients were evaluated via the inclusion and exclusion criteria. Sixty-nine patients were alive at hospital discharge with a good neurological outcome (i.e., CPC 1 or 2). The multivariate logistic regression model showed that prehospital time (time from EMS contact to hospital arrival) was an independent predictor for hospital discharge with good neurological outcome, in addition to age, bystander CPR, initial rhythm, and cause of cardiac arrest. The GAM plot showed that the adjusted odds ratio of prehospital time for the good neurological outcome was decreased linearly according to time, and the threshold was approximately 30 min. CONCLUSION: The threshold of allowable prehospital time, including field activity and transport, for OHCA patients might be 30 min at least in a Japanese urban setting.