Abstract: There are many categories of emotional and behavioral disorders among pupils but this study focused on oppositional defiance disorder and how it is affecting academic performance in Kisii South Sub County in Kisii County Kenya. Target population was 89 primary schools which was purposively selected based on researcher’s judgement and familiarity. The researcher selected the samples using stratified random sampling. Data collection methods were interview, questionnaires, observation schedules and FGD. Quantitative data was analysed using frequency counts, percentages, and descriptive statistics in the form of tables using SPSS, and qualitative data was analysed thematically.