In recent years, large-scale sports events have been held in Japan, making it necessary to ensure a strategic and systematic emergency medical system in stadiums. This study aimed to clarify the characteristics of emergency medical care at stadiums and sports facilities in Japan. Methods: This cross-sectional study used national emergency transport data recorded from 2015 to 2019. The study population included all emergency transport cases that occurred at athletic fields, stadiums, and sports facilities throughout Japan. Cases during competition were classified into sports-related emergency transport incidents (SrETi) and non-SrETi (NSrETi). Multivariable logistic regression analysis was used to examine factors associated with severity. Results: In total, 26,710,631 individuals were registered (14,078 SrETi, 15,458 NSrETi, 29,536 total). In the SrETi group, nine participants (0.06%) died, four (0.03%) became seriously ill, and 313 (2.22%) sustained serious injuries. In the NSrETi group, 92 participants (0.60%) died, 17 (0.10%) became seriously ill, and 882 (5.71%) sustained serious injuries. Factors associated with the severity of injuries included being in the NSrETi group (adjusted odds ratio [AOR], 1.52; 95% confidence interval [CI], 1.29-1.76) and the incident taking place in a toilet (AOR, 1.84; 95% CI, 1.09-3.12), a swimming pool (AOR, 3.67; 95% CI, 2.83-4.77), or other locations (AOR, 1.26; 95% CI, 1.08-1.46) (vs. the ground). Conclusion: Severe illnesses and injuries occurred not only among competitors but also among non-athletes (e.g., spectators and staff). Training of first responders and strategic placement of automated external defibrillators should also be considered for future sports events.