This study investigated effects of in-service training on effective classroom control and teachers'- students' relationship in secondary schools in Edo State. A descriptive survey using an ex-post facto research design was adopted. Stratified and simple sampling techniques were utilized to determine the sample size. The respondents were two hundred and eighty (280) principals, vice principals and heads of department from selected public secondary schools in Edo Central Senatorial District. The instrument for data collection was a 10 item structured questionnaire. Data were collected and analysed using percentages and frequency counts. The instrument for data collection was a 10 item structured questionnaire. The findings of the study showed that in-service training has significantly affects effective classroom control and teachers'-students' relationship. It was therefore recommended that in-service training should be regularly organized for teachers in secondary schools.