Objectives: The aim of this study was to pilot a test of the effectiveness of school-based humanistic counselling (SBHC) in an ethnically diverse group of young people (aged 11-18 years old), with follow-up assessments at 6 and 9 months. Design: Pilot randomized controlled trial, using linear-mixed effect modelling and intention-to-treat analysis to compare changes in levels of psychological distress for participants in SBHC against usual care (UC). Trial registration: ISRCTN44253140. Methods: In total, 64 young people were randomized to either SBHC or UC. Participants were aged between 11 and 18 (M = 14.2, SD = 1.8), with 78.1% of a non-white ethnicity. The primary outcome was psychological distress at 6 weeks (mid-therapy), 12 weeks (end of therapy), 6-month follow-up and 9-month follow-up. Secondary measures included emotional symptoms, self-esteem and attainment of personal goals. Results: Recruitment and retention rates for the study were acceptable. Participants in the SBHC condition, as compared with participants in the UC condition, showed greater reductions in psychological distress and emotional symptoms, and greater improvements in self-esteem, over time. However, at follow-up, only emotional symptoms showed significant differences across groups. Conclusions: The study adds to the pool of evidence suggesting that SBHC can be tested and that it brings about short-term reductions in psychological and emotional distress in young people, across ethnicities. However, there is no evidence of longer-term effects.