The present study compares the effects of the cooperative jigsaw II method and traditional teacher-centred teaching method on improving vocabulary knowledge and active-passive voice in English as a foreign language for engineering students and the students' attitudes towards learning English. Jigsaw is a cooperative learning model that involves small groups of 5-6 students teaching each other subject matter with success dependent upon student cooperation. Sixty-six engineering students participated in the study and a pre-test-post-test control group experimental design was employed. The students were randomly assigned into two groups: an experimental group and a control group. The experimental group used cooperative Jigsaw II as an instruction method while the control group used traditional teacher-centred instruction. The groups were administered an achievement test, as a pre-, post- and delayed post-test. The results revealed statistically significant differences in favour of the experimental group on the dependent variables of improving vocabulary knowledge and learning active-passive voice in English. The attitude scale results showed that the cooperative learning experience had a significant positive effect on engineering students' attitudes towards learning English and promoted better interactions among students as well. (Contains 5 tables.)