The jigsaw model is a dynamic cooperative learning approach where students become experts on different segments of the material and teach their peers, thereby enhancing engagement accountability, team work, and ultimately improving academic achievement. This study investigated the effectiveness of a cooperative learning strategy on secondary school students' biology achievement using the jigsaw learning model. A quasi-experimental, nonequivalent control group pretest-posttest design was employed, involving two secondary schools. One school (n = 40 students) was randomly assigned to the intervention group, while the other (n = 41 students) served as the control group. Data were collected through achievement tests, with a pretest administered to both groups before the intervention. Analysis of the pretest data revealed that no significant difference in biology scores between the two groups (mean difference = 4, ES = 0.02, p > 0.05). After a 16-week intervention, the cooperative learning strategy using the jigsaw model resulted in a statistically significant improvement in the experimental group's post-test performance (mean difference = 19.2, ES = 0.33, p < 0.05). However, the intervention showed no notable impact on gender-based post-test achievement scores among experimental group participants (mean difference = 2.2, ES = 0.008, p > 0.05). Therefore, the study affirmed that cooperative learning strategy, specifically employing the jigsaw model, is a valid and effective approach for secondary school biology.