Due to high dropout rates (30%) among first-year students, our college of engineering operates programmes for promoting students' retention and learning. The peer-led team learning (PLTL) programme accompanies Science, Technology, Engineering and Mathematics introductory courses with a high rate of failures, and incorporates workshops of small groups of students for developing active-learning and problem-solving skills. The workshops are led by outstanding students from advanced years; the peer leaders (PL). This study focused on the effects of the PLTL programme (40 workshops, 26 PLs) on the achievements of students who participated in the workshops compared with those who did not, and on its impact on the PLs. Findings reveal that workshops advance students of all levels and improve their achievements in several courses, while contributing more to students with higher academic capabilities. PLs felt satisfaction and believe they have gained self-confidence, and mentoring and communication skills for their future careers.