The study investigated the influence of learner participation in education-based and sport-based co-curricular activities on academic performance in public secondary schools in West Pokot County, Kenya. Grounded in Austin’s theory of involvement, it employed a mixed-method approach and a convergent mixed research design. The target population included 50 principals, 200 co-curricular teachers, and 826 form three students from 50 schools. A sample of 277 respondents (232 students, 36 teachers, and 9 principals) was selected using simple random and purposive sampling techniques. Data was collected through questionnaires and interviews and analyzed descriptively and thematically. Findings revealed that academic clubs (36.2%), debate clubs (20.7%), and field trips were the most popular education-based co-curricular activities, while article writing (1.7%) and symposiums (3.4%) had the least participation. Athletics and football were the most widely offered sports, while handball, volleyball, basketball, netball, and table tennis were limited due to inadequate resources and expertise. Students participated more in athletics and football, which, along with other sports, positively influenced academic performance. Music, drama, scouting, and guiding were also widely available and had high participation rates. The study concluded that both education-based and sports-based co-curricular activities positively impacted academic performance. However, resource constraints limited access to certain activities. It recommended proactive planning and management by school principals and teachers to enhance intellectual growth. Schools should improve sports facilities, train teachers, and diversify clubs to include public speaking, poetry, and photography. These recommendations aim to integrate co-curricular activities more effectively into education, benefiting all stakeholders.