The study evaluated the effects of teachers' professional and pedagogical competencies on implementing cooperative learning method and enhancing students' learning engagement and outcomes in science. The study employed randomized controlled trials method. The pretest-posttest data were analyzed by using two-tailed t-test and ANCOVA to either reject or not reject the formulated hypotheses at the p 0.05 level of significance. The findings indicated that the implementation of cooperative learning method resulted in students' authentic learning engagement and higher academic achievements in science compared to individualistic lecture method where the differences between the baseline, mid-line and end-line showed significant increase because of teachers' professional learning practices to develop and update competencies and skills. Proper utilization of cooperative learning in classrooms helps to accommodate heterogeneity of students from diverse background ahead of ensuring learning engagement. The natural science teachers exposed to cooperative learning method developed better professional competencies and skills like content-knowledge, pedagogical skills, beliefs and attitudes compared to those who were not exposed to it. Thus, there were direct relationships between utilization of cooperative learning method and students' learning engagement and outcomes in science. The finding summarized that teachers' professional learning interventions improve implementation of cooperative learning method in classrooms. Thus, cooperative learning method persuades students' learning collaboratively and individually to promote higher order thinking, learning and responsive creativity. Teachers' continuous professional development practices should be implemented to improve their professional and pedagogical competencies and students' interdependence, individualistic accountability, communication skills, group processing skills and students' learning engagement.