This study investigated the effects of computer-assisted Jigsaw II cooperative strategy on physics achievement and retention. The study also determined how moderating variables of achievement levels as it affects students' performance in physics when Jigsaw II cooperative learning is used as an instructional strategy. Purposive sampling technique was used to select two senior secondary school class II (SSSII) physics students from two intact classes in Minna, Niger State, Nigeria. Eighty students from two intact classes were assigned into Jigsaw II and Individualized Computer Instruction (ICI) groups. Computer-Assisted Learning Package (CALP) on physics and Physics Achievement Test (PAT) were used as treatment and test instruments. Analysis of Covariance and Scheffe's test were used for data analysis. Findings indicated that students taught physics using computer-assisted Jigsaw II performed better and retained the physics concepts longer than those taught using individualized computer instruction. In addition, achievement levels had significant influence on their performance. Based on the findings, it was recommended among other that physics teachers should be encouraged use computer-assisted Jigsaw II cooperative strategy to enhanced students' performance.