Social media influencers (SMIs) have become an important source of health information for adolescents. However, the lack of expertise and commercial interests of SMIs pose challenges for adolescent health. To gain a better understanding of these challenges, this scoping review aimed to synthesize existing research on the role of SMIs in adolescent health. Using the PRISMA-ScR approach, we conducted a comprehensive search of eight databases and screened articles based on predefined criteria. The final sample included 51 articles published between 2012 and 2022. Results revealed inconsistent definitions and classifications of SMIs. The most common topics included appearance, nutrition, and substance use, while mental and sexual health topics were underrepresented. The ability of SMIs to establish trustworthy relationships with their followers was highlighted in the reviewed studies, shedding light on potential benefits and challenges for adolescent health. However, most studies focused on the negative roles of SMIs, such as the promotion of unrealistic body images, unhealthy diets, substance use, and inaccurate diagnosis and treatment advice. In addition, inappropriate advertising of unhealthy products (e.g., junk food, tobacco products and alcohol) was identified as a major challenge. The reviewed studies identified stricter regulation and improved social media and health literacy as important avenues for policy action. Less attention was given to the potential positive impact of SMIs and how to effectively include them in health promotion campaigns. In addition, the majority of studies were conducted in the Global North and relied on quantitative approaches, resulting in a lack of representation of minority populations and male adolescents.