The study of determinants of university students’ performance has been an ongoing research in the last decade. Whether or not class attendance is a major factor has been debated over the years, but the empirical studies have been few and inconclusive. This study investigated the impact of classroom attendance on academic performance of university students in an Organic Chemistry course. It also looked into the moderating effect of gender on attendance and academic performance. Data was collected through expo-facto survey involving real time documentation of attendance for each student at each class lesson throughout a particular (3 months) semester. Data collected were analyzed using the Statistical Package for Social Sciences (SPSS) 17.0 to present the descriptive and inferential statistics. The results revealed a significant effect of attendance marks on academic scores at p<0.05 (t=0.00). However there was no significant effect of gender on academic scores (t=0.484), p<0.005 and also, no significant effect of gender on attendance (t=0.986) at p<0.05. Recommendations were made for policies and classroom practices that would improve class attendance of university students.