Studies have shown that cognitive behavioral therapy may be a useful method for alleviating the symptoms of depression. Depression is a growing issue among college adolescents in Nigeria. This study examined the effects of group cognitive behavioural therapy on depressive symptoms in a sample of college adolescents. We employed a randomized controlled trial design with 162 college adolescents in Southeastern region of Nigeria. One screening tool was used to ascertain the severity of depressive symptoms among the study participants at pre-treatment, post-treatment, and follow-up evaluations. In order to analyze the data collected, repeated measures analysis of variance and t test statistics were employed. Effect size of the intervention was determined using partial eta squared. The findings of the experiment showed that level of depressive symptoms of adolescents enrolled in the group cognitive behavioural therapy group was significantly reduced compared to the waitlisted control group at post-treatment evaluation. We also found that this significant reduction in depressive symptoms was maintained at follow-up.