A visible difference to the face or body may challenge adolescents’ adjustment and engagement in life activities, where some require psychosocial support. However, evidence is limited for whether existing interventions for this adolescent group reduce social or appearance-related distress. We therefore conducted a parallel-group, randomised control trial to evaluate the effectiveness of Young Person’s Face IT, a self-guided web-based psychosocial intervention developed for adolescents with a visible difference who experience distress. Adolescents (N = 189, aged 11–18) from two countries (Norway and the Netherlands), were randomly allocated to an intervention group or care as usual (CAU). Outcomes were body esteem, social anxiety, perceived stigmatisation, and life disengagement. Compared with CAU, participants who completed Young Person’s Face IT showed reductions in social anxiety symptoms (ηp2 = 0.06). No significant improvements were found for the other outcomes. This study endorses web-based psychosocial support in reducing social anxiety in adolescents distressed by a visible difference. Future studies are needed to confirm the effectiveness of Young Person’s Face IT and to explore potential long-term effects.