Objectives This study aimed to update the scientific knowledge concerning the relationship between the use of social networking sites and body image among adolescents. Methods A preregistered systematic review was conducted following PRISMA guidelines and allowed to include 30 peer-reviewed articles for qualitative analysis, consisting of 26 unique samples (n=31,331; Mage=14.89; SDage=1.07). The search was conducted on Pubmed, PsychInfo and Scopus focusing on studies that included any social network site use and body image measures while being based on general population adolescent samples. Social networking site use referred: 1) to any online activities such as browsing, posting, editing selfies, liking, commenting; 2) to any exposure to appearance-related content; or 3) to a measure of frequency use. The scope of social networking sites considered in the present review was extended to online video-sharing platforms and online dating applications due to their relationship with appearance. Body image as considered through MeSH terms referred to a wide range of possible outcomes including body and facial dissatisfaction, dysmorphophobia, body surveillance, self-objectification, body shame, weight concerns, self-monitoring. Any mental health outcome was extracted when available although its absence was not an exclusion criterion.. Results Among the 30 studies included in the review, 22 were cross-sectional, seven were longitudinal and one had an experimental design. Overall, among studies based on unique samples, 18 studies included both males and females (n=28,081; Mage 14.84; SDage=1.06), seven were based exclusively on female samples (n=2,507; Mage 14.87; SDage=1.19), while one study recruited only male adolescents (n=743; Mage 15.90; SDage=0.54). Only six studies were based on representative samples. These studies reported a robust association between frequency of social networking site use and negative body image among both females and males. In addition, exposure to appearance-related content was also deleterious to body image. The association between the use of social media and negative body image may involve negative mental health outcomes, such as depressive symptoms, low body esteem and problematic use of social media. Measuring specific activities on social network sites or exposure to appearance-related content (e.g. selfies editing; selfies posting) may be more accurate than using a frequency of overall use (e.g. during the past month) when predicting body image. Studies addressing underlying processes supported that the relationship between use of social media and body image may not be direct but rather involve intermediary steps on both cognitive and social levels, namely internalization of the thin ideal, self-objectification, peer appearance-related feedback, ascendant social comparison with peers and celebrities. Also, it remains unclear whether mental health mediates this relationship. Conclusions The association between the use of social networking sites and negative body image is robustly supported in the literature. However, studies measuring frequency of overall use may instead be predicting negative body image with a nested measure of the use of social network sites, namely specific activities involving appearance-related content. Due to the observed discrepancies between self-reported frequency of social networking site use and actual use in methodological literature, future research may rather measure behaviors commonly encountered on a given platform. Furthermore, there is a need to distinguish specific site categories such as highly visual social media when focusing on body image outcomes. . Focusing on specific social media platforms may in turn lead to more targeted prevention regarding a safe utilization of social networking sites among adolescents. Despite the growing body of research concerning the association between social media and body image, the current review underlines that additional longitudinal and experimental studies are needed to investigate potential bidirectional effects, as well as studies based on representative samples to improve generalization to adolescent populations.