The present study attempts to gauge the effect of individualized instructional methods as a reinforcement strategy for mastery learning. Among various individualized instructional methods, the study focuses on PIM (Programmed Instructional Method) and CAIM (Computer Assisted Instruction Method). Mastery learning is a process where students achieve the same level of content mastery but at different time intervals. It is an instructional philosophy based on the belief that all students can learn if given the appropriate amount of time and the appropriate instructional opportunities [Koul Lokesh and Sharma (1994)]. The study has employed the conventional teaching method followed by the individualized instructional methods (as reinforcement strategies). The study adopts the Quasi-experimental research method with "Group at hand" sampling method. The samples are selected from three higher secondary schools in Tamil Nadu and Kerala (States in South India). After conducting three experimental phases the study concludes that individualized instructional methods (PIM & CIAM) are very effective as a reinforcement strategy for mastery learning.