The main aim of present investigation was to find out the effect of mastery learning strategies viz. Bloom‟s Learning For Mastery (LFM) and Keller’s Personalized System of Instruction (PSI) on concept attainment in geometry among high school students. For achieving the objectives of this study, a random sample of 105 students studying in 9th class was selected and “Three Groups: Randomized Matched Subject Pretest-Posttest Design” was employed. The sampled students were divided into three homogeneous groups on the basis of their non-verbal intelligence level by administering Raven’s Standard Progressive Matrices (SPM). The first group and second group were taught through Bloom‟s LFM and Keller’s PSI respectively and thus, termed as experimental groups. The third group was imparted instruction through conventional method of teaching and named as control group. The data were collected by administering self-developed concept attainment test in geometry. The statistical technique of „Analysis of Co-Variance (ANCOVA)‟ was employed to analyze the data. The results revealed that both Bloom‟s LFM and Keller’s PSI were significantly more effective in attainment of geometrical concepts as compared to conventional method of teaching. It was further inferred that Bloom‟s LFM was significantly better in attainment of geometrical concepts in comparison to Keller’s PSI.