Background: Basic life support (BLS) is one of the keys to saving lives following a cardiac arrest and poor outcomes have been shown as the result of delayed BLS. Cardiac arrests more often occur outside of the hospital, making the first-responder layperson that was present at the scene the key to the success of the chain of survival. Knowledge is important in the learning process, thus for non-medical individuals to be able to give proper BLS, they need sufficient knowledge regarding BLS itself. Objectives: To assess the knowledge of non-medical individuals in Surabaya regarding BLS. Method: A descriptive cross-sectional study using a questionnaire to assess the respondents' knowledge regarding BLS. Results: For the high school students group, all questions need to be eliminated (p>0.05). While for the university students group, all questions can be kept and most of them scored 56.25%. For the workers group, some questions need to be eliminated (p>0.05) and when compared to the university students, there is no significant difference (p>0.05) between the two groups' knowledge regarding the common questions. Conclusion: High school students in Surabaya do not have adequate knowledge regarding BLS. While the knowledge of non-medical university students in Surabaya regarding BLS is the highest among other groups of this research. As for the knowledge of non-medical workers in Surabaya regarding BLS, it is lower than university students, although there is no significant difference in both groups' knowledge regarding cardiac arrest findings.