The study investigated the influence of teachers' characteristics on students' performance in Computer Studies. The ex-post-facto research design was used in the study. Descriptive data gathered through questionnaires were analyzed using percentages, means and standard deviations. Hypotheses were tested using the Chi square statistic and the Pearson Product Moment Correlation Coefficient. The study found a weak relationship between the Computer Studies teachers' level of education, training levels in Computer Studies and teaching experience and students' performance in Computer Studies. However, there was a strong relationship between the Computer Studies teachers' attitude and students' performance in Computer Studies. It was thus concluded that the Computer Studies teachers' level of education, training levels in Computer Studies, teaching experience and attitude towards Computer Studies influenced students' performance in Computer Studies. The study recommends further researchbe conducted on the effect of the attitudes of school administration and students towards Computer Studies on students' performance in Computer Studies in secondary schools in Kenya.