There have been efforts aimed at solving student behaviour problems in secondary schools in Kenya. However, this has realized very little achievement. The current study investigated the effectiveness of guidance and counseling in the management of student behaviour in secondary schools in Kenya. The study was informed by assertive discipline model. Mixed method approach with concurrent triangulation design was used for the study. The population of the study was composed of 431 teachers 40 heads of guidance and counseling and 40 Deputy Principals. Stratified random sampling technique was used to select teachers, deputy principals and heads of guidance and counseling. Krejcie and Morgan sample size determination table was used in the study to determine a sample size of 28 deputy principals, 28 heads of guidance and counseling and 196 teachers. Data was collected using questionnaires, interview schedules and document analysis guides. Reliability was ascertained through split half method, and a reliability coefficient of 0.871 was realized. In order to ensure face validity of the instruments, the researcher sought expert judgment from university lecturers. Descriptive statistics and correlational analysis were used to analyze quantitative data while qualitative data was analyzed using thematic framework. The study established that there was a correlation coefficient of r=0.503 between guidance and counselling and the management of student behaviour. The findings of the current study may help the Ministry of education in the formulation of policies relevant to the management of student behaviour in secondary schools.