Twenty-first century classrooms have come with a lot of changes in the instructional delivery at various levels of education. However, most teachers in Nigerian still adopt the traditional method of instruction not minding the demands of the twenty-first century classrooms. As a result of this, there is dearth of empirical evidence on the impact of computerassisted instruction on the students' achievement in mathematics and physics. This study, therefore, evaluated the impact of computer-assisted instruction (CAI) on mathematics and physics students' achievement. Quasi-experimental, nonequivalent groups design was adopted for the study using a sample of 200 participants. Mathematics Achievement Test (MAT) and Physics Achievement Test (PAT) were used to collect data for the study. The internal consistency reliability indices of the MAT and PAT were estimated as 0.89 and 0.75 respectively using Kuder-Richardson formula 20. The hypotheses were tested at 0.05 levels of significance using analysis of covariance. It was found that Computer-Assisted Instruction (CAI) significantly improved mathematics and physics students' achievement. This finding has implication for Industrial Technical Education for the fact that improved achievement of students in mathematics and physics subjects at secondary education level will enable them to have interest in industrial technical education at higher education. Thus, Mathematics and Physics teachers should be trained on how to master the techniques needed for the preparation and use of the CAI package for effective teaching and learning of different concepts in Mathematics and physics.