First aid is one of the most important life-saving skills a health provider specifically or anybody generally must have. It can be defined as the first treatment one provides at the site of the accident to the injured person until full medical treatment is available. In some emergency situations, simple first aid can make a life-or-death difference. Aim. This study is designed to evaluate the knowledge of first aid among medical students at KSAU-HS in Riyadh, Saudi Arabia. Methods. The cross-sectional study is conducted in KSAU-HS, Riyadh, about the knowledge of first aid among medical students. A self-administered structured questionnaire is used for the purpose of data collection. The main variables are as follows: to compare the knowledge of first aid between male and female medical students, among different years of study, and identify the percentage that have knowledge of first aid. Results. Out of 326 students, 10 students (3.1%) scored excellent, 99 (30.4%) good, 136 (41.7%) average, 75 (23%) poor, and 6 (1.8%) very poor. Conclusion. The level of knowledge improved with the advancement in years, but this was not sufficient, and more training should be given to all medical students on first aid.