This study investigated the effect of Mastery Learning Approach (MLA) and Mind Mapping Approach (MMA) in improving students' academic performance in Physics and also determined their effect in enhancing students' retention of Physics. These were with a view to ascertaining the best teaching method for improving students' learning outcomes in Physics. The study adopted the non-equivalent pre-test, post-test control group experimental design. Simple random sampling technique was used to select three co-educational secondary schools in Ikere Local Government Area of Ekiti State in Nigeria. The sample for the study was 74 senior secondary school one (SSS1) Physics students from the three selected secondary schools. Three intact classes were used for the study. The instrument used for data collection was "Physics Achievement and Retention Test" (PART). Data collected were analyzed using t-test and analysis of variance (ANOVA). The results showed that there was a significant effect of treatment on the academic performance of students taught with MLA, MMA and conventional method with students taught using MMA showing the best academic performance, followed by MLA and then Conventional. Also, no significant effect of treatment was found in the retention ability of students taught with MLA and MMA with students from both methods having nearly the same mean score. The study concludes that both MLA and MMA could improve students' learning outcomes in Physics; however, MMA could improve students' learning outcomes better. It therefore recommends that ministry of education should organize training for science teachers especially Physics teachers on how best they can adopt these innovative teaching strategies during instruction so that learners would be guided to learn meaningfully and be assisted to retain what is learnt in Physics.