This study evaluates the impact of the peer-mentoring program implemented by a Chilean higher education institution on underrepresented students' academic success. Specifically, it assesses whether freshmen who enrolled in 2018 and took part in this initiative performed better than students with similar characteristics who did not. A quantitative quasi-experimental design was applied, using the Propensity Score Matching method. The results show that students who took part in this peer-mentoring program got better average grades and had better retention rates and attendance levels than those who did not. Strategies for developing successful mentoring initiatives for college students are discussed, with a special emphasis on their potential relevance to underrepresented students.