Aim of the work: basic life support (BLS) refers to the skills that require few tools to save lives of the victims of cardiac or respiratory arrests. All healthcare providers are required to master these skills in order to maximize the care to those who experience such emergencies. This study aimed to assess the knowledge and attitude toward BLS in King Abdul-Aziz University among 3^rd to 6^th year medical students. Methods: this is a retrospective cross-sectional study conducted in King Abdul-Aziz University, College of Medicine in Jeddah-Saudi Arabia among the medical students, from June to October 2016 lasting for a period of 4 months. Data were gathered by using electronic Google forms questionnaires that were distributed to 3^rd, 4^th, 5^th and 6^th years medical students. Data analysis was done by using SPSS version 17 in July 2017 Results: 370 medical students at King Abdul-Aziz University (KAU) were participated to evaluate their knowledge and attitude toward Basic Life Support (BLS). 190 of the students were male students. 43% and 38.5% of female and male students scored all the right answers respectively. Both the total mean of correct answers of knowledge and attitude toward BLS were 40% for both variables. Students who had BLS courses other than the mandatory ones scored 41.5% of the correct answers, while the students who had only mandatory BLS courses scored 39% of the correct answers. Conclusions: among KAU medical students, the data showed poor essential knowledge toward BLS. Overall attitude towards BLS was negative. However, the data also showed slight improvement when students had BLS courses other than the mandatory ones. Therefore, more focus may be placed for strengthening BLS skills. In addition, it is recommended to have an annual BLS simulation for all medical students to consolidate their skills and knowledge. We also recommend adding active learning to all medical students.