Peer-led Team Learning (PLTL) is an instructional method reported to increase student learning in STEM courses. As mathematics is a significant hurdle for many freshmen engineering students, a PLTL program was implemented for students to attempt to improve their course performance. Here, an analysis of PLTL for freshmen engineering students in mathematics courses over three years is presented. Particular issues of concern are (1) if more participation in PLTL groups aids student performance to a greater extent, and (2) if students who participate frequently in PLTL groups achieve more success in their math courses. Student performance in their math courses was evaluated through their course grades. The level of participation by the students in their PLTL groups was determined through weekly attendance reports, with mentors assuring that all students participated fully while present. Grade comparisons were made both between participants who attended different numbers of group sessions and between participants and non-participants in their courses. Analysis of the first year of the program suggests that increased participation in the PLTL groups correlates to better course performance. Data from the last two years indicate that statistically significant subject mastery is achieved by PLTL participants in Calculus I courses; however, while Pre-Calculus level students show some improvement, the results are less significant. In general, it is found that greater participation in PLTL groups is beneficial for many students. PLTL groups offer educational benefits to many students, but participation does not guarantee improvements for all students.