Personal trainers (PTs) and professionals working in the physical activity (PA) sector are increasingly recognized as important for promoting PA and mental health (MH). Within a post-secondary context, the importance of such professionals is made evident by rising awareness of the benefits associated with PA referral systems and tailored programs for promoting student MH. Yet, evidence remains sparse regarding whether on-campus PTs feel adequately equipped and competent to promote MH within their professional practice. As such, within a post-secondary context the current study aimed to (1) explore PTs' competency beliefs and attitudes towards promoting MH, and (2) explore PTs' perspectives towards their education and training on PA and MH. Eight PTs (50% women; Myears of PT experience = 4.81 years) were purposefully sampled and participated in semi-structured interviews. Using thematic analysis, three themes were identified: (i) personal training and MH promotion: a missed opportunity; (ii) perceived scope of practice and professional role and responsibilities, and (iii) need for MH training and standards of practice. Based on the results, PTs recognized the importance of PA for promoting MH. However, limitations regarding MH education and uncertainties surrounding professional responsibilities and scope of practice were noted. Current results underscore a need to improve training opportunities and initiatives to enhance on-campus PTs' knowledge and awareness on PA and MH. This research is important for advancing our practical understanding of strategies to help integrate on-campus PA services and professionals within the promotion of post-secondary student MH.