This paper reports on the results of an action research to explore the effectiveness of using cooperative learning strategies on students' academic achievement, their understanding of physics concepts and their motivation to learn in the physics classroom. The study involved a secondary four express physics class of 41 students in a neighbourhood school. Various cooperative learning structures were used to teach the topics on "Current Electricity" and "D.C. Circuits" over a period of about 8 weeks. During this period, teacher-crafted pre- and post-intervention tests were administered to the class. A questionnaire survey was used to examine students' motivation to learn and perceptions of their learning experiences before and after the treatment period. A class using traditional method of teaching was also involved in the study as a control. The effects of using cooperative learning on students' academic achievement and their motivation to learn were examined through the analysis of the results of the pre- and post-tests and students' perception surveys, while the extent of using cooperative learning on helping students achieve a better understanding of physics concepts was examined through the qualitative analysis of the students' journals. The results showed that the use of cooperative learning does increase students' academic achievement helps students to achieve a better understanding of physics concepts and increases students' motivation to learn. (Contains 4 tables, 3 figures and 1 footnote.)