The purpose of the study was to investigate the influence of monitoring and evaluation on effective teaching and learning in secondary schools in Githunguri district. This study was guided by the following objectives: To establish the effect of lesson preparation, teaching and learning process, monitoring of school attendance for teachers and students impact on teaching and learning process, effect of evaluation process used in schools on effectiveness of teaching and learning and to establish the effect of learning and teaching environment on the effectiveness of teaching and learning. The study adopted survey research design. The study targeted 30 principals, 750 teachers, 150 HODs and 120 class prefects 1 class prefect per stream in the 30 public secondary schools in Githunguri district. The researcher used simple random sampling techniques to sample the 187 respondents. The study had a sample size of 15 principals, 113 teachers, 23 HODs and 36 class prefects; a total sample of 187 respondents. The sampling technique was random. Questionnaires were used for the data collection from the HODs, teachers and class prefects. Interview schedule was used for the principal. Validity of the research instruments was ensured by undertaking a pre-test in 2 schools which were not included in the study. The researcher also discussed the instruments with the supervisor to ascertain there validity. Reliability was ensured through calculating the Cronbach coefficient. The research utilized descriptive analysis of each of the questions asked in the questionnaires presenting them in tables and graphs. There should be improvement on lesson preparation process, the schools should improve on the monitoring of school attendance for teachers and students as it has an impact on teaching and learning process. The finding of the study will provide invaluable insight into the role of monitoring and evaluation by principals on effective teaching and learning in secondary schools. This will help policy makers in formulating policies to guide the monitoring and evaluation process in secondary schools.