Background: Young adults with intellectual and/or developmental disabilities lack access to mental health supports. Peer-delivered services may fill this gap. We adapted a theory-driven and evidence-based peer mentoring intervention for virtual-delivery and investigated its acceptability and participants' preliminary response. Methods: Twelve young adults with intellectual and/or developmental disabilities participated in the 16-week intervention and completed outcome measures at pre-mentoring, post-mentoring and 1-month follow-up. To evaluate acceptability, participants completed interviews and a survey. Preliminary response was measured with the Alexithymia Questionnaire for Children and PROMIS short forms (Self-efficacy for Managing Emotions, Anxiety, and Physical Stress). Results: Participants felt emotionally supported, increased self-understanding, and learned to use coping strategies. Participants reported improvements in alexithymia, self-efficacy for managing emotions and anxiety; no changes were observed for physical stress symptoms. Conclusions: Participants were satisfied with peer mentoring and data suggest it may have promise to support development of skills that support mental health outcomes.