This study investigated the effect of reciprocal peer counselling in the enhancement of self-concept of Nigerian adolescent students. The effect of sex on self-concept was also investigated. Sixty-eight senior secondary school students from three schools (a boys' school, a girls' school, and a co-educational school) in Benin City, Edo State participated in the study. A 40-item, 5-point Likert scale (an adolescent self-concept inventory) was the instrument used to elicit responses on self-concept from the subjects before and after treatment. Results indicated that subjects in the treatment group had significantly higher post-test self-concept scores than the control group (obtained t of 6.58 is greater than the critical t-value of 1.96 with df = 66 at alpha level of 0.05). Furthermore, results also indicated that there was no significant effect of sex on the self-concept of these adolescent students (obtained t-valve of 0.17 is less than the critical t-value of 1.96 with df = 66 at alpha level of 0.05). In sum, the present study provides evidence that reciprocal peer counselling is an effective intervention for the enhancement of self-concept. It is recommended that this therapy be used in the enhancement of self-concept among adolescents. (Contains 4 tables.)