This meta-analytic study compared the effect of peer-led learning versus non peer-led learning on students' cognitive achievement in post-secondary education. Twenty-eight studies published in English from six countries between 1993 and 2017 were identified and used in the analysis. Result of the analysis on the random-effect model showed a moderate but positive effect, meaning that peer-led learning was associated with higher cognitive achievement than non-peer-led learning. Three study characteristics were examined including duration, student leaders' training, and task type. Only the task type was found significant in moderating the effect of peer-led learning. Student leaders' facilitation of problem-based learning tasks outperformed other types of tasks. Results of this study not only provided suggestions for peer-led learning designers and coordinators but also called for future research of student leaders' readiness as well as online peer-led learning.