ABSTRACT The purpose of this study was to investigate the effectiveness of group work in teaching and learning mathematics in the selected secondary schools in Mombassa island Mombassa District, Kenya Specific Objectives of the study were: find out the school related factors that hinder the implementation of group work in secondary schools, find out the different forms of group work in secondary schools, and find out what the attitudes of students towards group work in secondary schools. The methods used for data collection were interview guides to the learners. The findings revealed that The findings indicated that lack of teachers' efforts to form the groups was the major factor that hindered implementation of group work since groups were mainly formed by the teachers, the ideal form of group work was by students themselves and not the teachers and that all the students had a positive attitude towards the formation of group work. The study recommended that, government should make it a policy to encourage the formation of group work as a teaching 1nethod especially in science subjects like 1nathematics which students consider to be hard, teachers should encourage the students to form their own groups so long as they are careful not to choose group members who are not serious with the intention of the group formation. Students should be encouraged to form groups in order to encourage the1n to achieve good academic results in mathematics and indeed in other subjects