Cooperative learning is a strategy to teach students by adopting different teaching methods. It affects different aspects of students learning process. Cognitive engagement is one of the most important aspects of students learning process which is greatly affected by this strategy. This study finds the effect of this strategy on cognitive engagement of the secondary school students. It was an experimental study in nature. 50 students of 10th class were selected as the sample of the study by using convenient sampling. Control group was comprised of twenty-five (25) students. Experimental group was also comprised of twenty-five (25) students. Team Assisted Individualization (TAI) method of cooperative learning and traditional method were used to teach the students of experimental group and control group respectively. This experiment was lasted for six weeks. Pretest and posttest control group design was used. The cognitive engagement scale developed by Kong Wong and Lam (2003) was employed. Independent Sample t-test was used to make analysis of the collected data. This study claimed that cooperative learning had significant effect on cognitive engagement. Experimental group learnt significantly higher than control group.