Problem-based learning is an active student-centred approach, which requires engineering students to work together in solving real-world problems. This study aims to review the incorporation of cooperative learning principles in an introductory first-year engineering course that aimed to develop students' group skills while working on problem-based projects. A total of 367 students participated in 65 groups. No formal examination was written, as this course only consists of practical work. Data collection included an assessment matrix and reflective sheets where students' individual and group contribution to the project were recorded. The data were structured and visually integrated into tables. Based on the findings, this research suggests that the integration of cooperative learning principles enhanced the development of essential group skills and team performance in some of the groups while working on real-world engineering projects.