The Purpose of This Study Is to Examine the Effects of Parental Monitoring On Academic Achievement of Secondary School Students in Busia Sub-County. Expost-Facto Design Was Used in This Study with A Target Population of 23 Principals of Secondary Schools in The Sub-County, 188 Secondary School Teachers, 5726 Students and 4295 Parents. The Research Employed Simple Random Sampling to Select Students and Parents. Purposive sampling Was Used to Select Schools. Saturated sampling Was Used to Sample Principals. All Teachers in The Sampled Schools Were Considered. This Gave a Total of 7 Schools, 58 Teachers, 172 Students, 129 Parents, And 23 Principals. This Gave a Total of 382 Respondents Representing 10% Of The Target Population. Questionnaires and Interview Schedules Were Used to Collect Data. Quantitative Data Collected Through Questionnaires Was Analysed Using Descriptive and Inferential Statistics with The Aid of Statistical Package for Social Sciences (Spss) Version 22 To Generate Percentages, Frequencies, Descriptive and Inferential Statistics. Qualitative Data Was Analysed Using Thematic Analysis. The Study Found That the Effect of Parental Monitoring and Academic Achievement Using Pearson Product Moment Correlation Showed a Strong Positive Correlation (R = 0.488) Which Was Statistically Significant As P = 0.029 (P < 0.05).