Abstract: Drug use has become prevalent today than any other time in Kenya. Youths are using drugs which modify their mental, emotional and behavioral functioning. In learning institutions, drug use may make students to have poor concentration in class, high rate of absenteeism and failure in exams leading to poor academic performance. The purpose of this study therefore was to investigate the influence of drug use on academic performance among secondary school students in Matinyani district. Descriptive survey was used in this study. Fourteen public secondary schools were involved with population of 1701 students. Purposive sampling was used in the sample selection to select 5 schools which included a girls’ boarding, a boys’ boarding school, a mixed day school, a mixed boarding school and a mixed day and a boarding school.