The aim of this study is to examine the effect of the mastery learning and traditional learning on students? academic success, retention, achievement and attitudes using meta-analysis methods. As a result of the meta-analytic examination, 10 national and international studies that were carried out between 2003-2014 including values of sampling size (n) belonging to experimental and control groups in order to calculate the effect size, mean (X) and standard deviation (sd) or data enabling the calculation of these values; that implemented the mastery learning model used a pre/post-test control group model, and finally studied the effect of this model on academic success, retention, achievement and attitudes were selected. All the statistical processes were undertaken using the Comp­rehensive Meta-Analysis (CMA) and the MetaWin programmes. Moreover, the inter-rater reliability of the studies was calculated separately to increasing the reliability of the results of the research which was determined to be found as 100%. Consequently, it was identified that mastery learning has a positive and significant effect on students? academic success(ES=1.360), retention(ES=1.666), achievement(ES=0.951) and attitudes(ES=0.940) in accordance with random effects models. Thus, it can be said that mastery learning is influential, with respect to students? academic success, retention, achievement and attitudes