Introduction: San Diego has one of the busiest international land border crossings in the world. The epidemiology of prehospital care at the San Diego (California, United States) - Tijuana (Baja California, Mexico) border crossings are previously unreported. Investigators sought to describe prehospital care provided at the San Diego border crossings. Methods: This was a cross-sectional, retrospective data collection from April 2014 to March 2017 evaluating prehospital provider (PHP) contacts at two international border crossing addresses in San Diego. The 9-1-1 dispatch center and first response were provided by a single municipal fire agency with ambulance transportation provided by a contracting private agency. Patient dispatch data and electronic patient care records were queried for patient demographics, PHP arrival time, incident complaint, assessment narrative, and treatments provided. Natural language processing techniques were applied to map the narrative to the National Library of Medicine’s Unified Medical Language System. Descriptive analysis was performed in the R software program. Results: A total of 6,261 PHP patient contacts were made at the two border crossings during the study period. 87% of the calls were at the San Ysidro border crossing compared to 13% at Otay Mesa. The population, composed of 50.8% males, had ages ranging from 0 days - 103 years old, with a median age of 45 years old. There were 606 (9.7%) pediatric patients (textless18 years) and 1,416 (22.6%) geriatric patients (textgreater65 years). The top three incident complaints were respiratory distress (830, 10.8%) blunt trauma (827, 10.7%) and abdominal pain (814, 10.6%), and the top 3 medications provided were oxygen (481, 7.7%), normal saline (393, 6.3%) and ondansetron (352, 5.6%). Conclusion: This was the first study of PHP assessment and care at the San Diego-Tijuana border crossings. We found a large diversity in patient ages. Respiratory distress and blunt trauma were the most frequent complaints and oxygen was the most frequent treatment. The busiest day of the week was Sunday, and the busiest month of the year was July. Our newly described findings may assist EMS agencies with optimizing staff, equipment, and training at international border crossings.