This This paper aimed to determine the effect of Computer Assisted Instruction (CAI) on automobile technology education students' academic performance and attitude in tertiary institutions of Nigeria. The design of this study was nonequivalent group, pre-test/post-test quasiexperimental design. The geographical area of the study was north-eastern region of Nigeria. The sample for the study comprised of 32 students offering automobile technology from the two intuitions involved in the study. The instruments used for data collection include Automobile Technology Pre & Post-test Achievement Test and Automobile Technology Attitude Questionnaire. Delivering the instruction with the aid of CAI package, effect size differences revealed that students' academic performance and attitude improved positively in favour of the experimental group. But, as indicted by t-test value the differences between the two groups were not significant in the academic performance and attitude of the automobile technology students in the tertiary institutions of Nigeria. Knowing whether the statistical test was significant is not the most important, but quantifying the strength of the difference between variables and determining to see whether the difference is meaningful in a practical sense matters. Therefore, this implied that using CAI will help in improving quality of education in tertiary institutions of Nigeria..