The present study is aimed at finding the effect of Instructional software program in the learning of grammar on the achievement of teacher training students of Namakkal District. Parallel group experimental method was adopted in this study. A sample of 80 students studying in the teacher training college were selected on the basis of their knowledge in English grammar. 40 students were involved in conventional learning of English grammar and another 40 were considered for learning grammar based on instructional media. The instrument of the study was an instructional software program used for teaching particular grammar items. Achievement test was used after establishing validity and reliability. It is evident from the analysis that instructional media played a significant role in the learning of English grammar. Experimental group students have made significant higher gains in learning grammar in comparison to conventional group students. In light of the findings of this study, it was recommended that English teachers use Computer Aided Instructions in their teaching.