BACKGROUND Cardiopulmonary resuscitation is usually taught in universities through theoretical lectures and simulations on mannequins with low retention of knowledge and skills. New teaching methodologies have been used to improve the learning, placing the student at the center of the process. Likewise, the outside community knows next to nothing about cardiopulmonary resuscitation. Patients who have an out-of-hospital cardiac arrest will die if the effective maneuvers are not promptly done. Learning by teaching could be a way to answer both requirements. It was therefore decided to evaluate whether the medical students' cardiopulmonary resuscitation performance would improve when they teach other people, and if those people could learn with them effectively. METHODS A non-randomized controlled trial was designed to assess whether teaching Basic Life Support would increase students' learning. Socially engaged, seeking to disseminate knowledge, 92 medical students were trained in Basic Life Support and who subsequently trained 240 community health professionals. The students performed theoretical and practical pre- and post-tests whereas the health professionals performed theoretical pre- and post-tests and one practical test. In order to assess the impact of teaching on students' learning, they were divided into two groups: a case group, with 53 students, reassessed after teaching health professionals, and a control group, with 39 students, reassessed before teaching. RESULTS The practical students' performance of the case group went from 13.3 ± 2.1 to 15.3 ± 1.2 (maximum = 17, p < 0.001) and theoretical from 10.1 ± 3.0 to 16.4 ± 1.7 (maximum = 20, p < 0.001) while the performance of the control group went from 14.4 ± 1.6 to 14.4 ± 1.4 (p = 0.877) and from 11.2 ± 2.6 to 15.0 ± 2.3 (p < 0.001), respectively. The theoretical performance of the health professionals changed from 7.9 ± 3.6 to 13.3 ± 3.2 (p < 0.001) and the practical performance was 11.7 ± 3.2. CONCLUSIONS The students who passed through the teaching activity had a theoretical and practical performance superior to that of the control group. The community was able to learn from the students. The study demonstrated that the didactic activity can be an effective methodology of learning, besides allowing the dissemination of knowledge. The University, going beyond its academic boundaries, performs its social responsibility.