Causal attributions and help-seeking is not well explored among adolescents, despite evidence of perceived causes for difficulties influencing how adults engage with treatment and seek help. This study reviewed extant literature to understand what adolescents at increased risk of developing mental health difficulties and those with clinically significant symptoms perceive to be the cause of emotional distress; to determine the extent to which perceived cause influences help-seeking; and to identify potential differences/commonalities between these groups. A systematic review and qualitative thematic synthesis were conducted. 3,691 articles were identified, 18 were eligible to be included and were synthesized using thematic synthesis. Six main themes related to perceived cause are reported. Three of those themes were shared between the clinical and at-risk groups: (1) challenging social factors and perceived difference, (2) problematic family dynamics, and (3) cause is complex and multifaceted. Three themes were not: (4) unfairness and perceived lack of agency and (5) concern for self and others, were exclusive to the at-risk group, and (6) coping with a mental health difficulty was exclusive to the clinical group. Four main themes related to causal attributions and help-seeking were found, including: (1) cause and implications for self-preservation; (2) the degree of personal and wider knowledge and understanding of cause; (3) perceived extent of control in managing cause; and (4) cause having potential to affect others. The findings of this review demonstrate that perceived cause for emotional distress plays a role in help-seeking among adolescent groups and highlights likely differences in how adolescents at-risk of mental health difficulties and those with clinically significant symptoms attribute cause for their difficulties and subsequently seek help. This has important implications for how to support young people experiencing or at risk of mental health difficulties and presents a strong case for pursuing more research in this area.