The study investigated the effects of mastery learning approach on secondary school students’ academic achievement in Physics in Ekiti West Local Government Area, Ekiti State, Nigeria. The research design adopted in the study was Pretest-Posttest Quasi- experimental. Purposive and stratified random sampling techniques was used to select a total sample of 100 Senior Secondary One (SSI) Physics students (50 each experimental and control group respectively) from four senior secondary schools in Ekiti West local Government Area, Ekiti State. The instrument used to collect relevant data from the subjects was Physics Achievement Test (PAT). The reliability of the instrument was determined through the split-half method with the reliability coefficient of 0.88. Three null hypotheses were formulated and tested at 0.05 level of significance. The data collected were analysed using t-test and Analysis of Covariance (ANCOVA) statistical analysis. The results of the analyses showed that no significant difference existed between the performances of students in experimental and control groups involved in the study at pretest. However, academic achievement in the experimental group at post-test was found to be significantly better than that of the control group. Based on the findings of the study, it was concluded that Mastery Learning Approach teaching strategy is more potent in boosting students’ achievement in Physics in secondary schools than the conventional method in vogue in the nation and It was recommended that the conventional method presently in use by Physics teachers should either be improved upon, modified or replaced with a modern teaching approach (as appropriate).