The study examined the relationship between sexual harassment and academic performance of girls in secondary schools in Namayumba Town Council. A cross-sectional survey design was employed with a sample of 303 participants comprising 275 female students, 5 school principals, 6 guidance counsellors, and 17 teachers. Data were collected using questionnaires and interview guides. Results revealed that 68.4% of female students experienced at least one form of sexual harassment, with verbal harassment being most prevalent (54.2%). A significant negative correlation (r = -0.623, p < 0.001) was found between sexual harassment experiences and academic performance. Students who experienced frequent harassment had significantly lower GPAs (2.1) compared to those who did not (3.4). The study concluded that sexual harassment substantially undermined girls' academic achievement. It was recommended that schools implement comprehensive anti-harassment policies, establish confidential reporting mechanisms, provide mandatory staff training, and strengthen guidance and counselling services to protect female students and enhance their educational outcomes.