ENIdentity formation is an important developmental process during adolescence. The interaction between adolescents’ gender identity, loneliness, and body dissatisfaction is a complex and multifaceted phenomenon. Adolescent gender identity issues are thought to be related to loneliness, and body dissatisfaction is a risk factor for greater loneliness. It can be hypothesized that adolescents experiencing gender identity issues could feel lonelier when experiencing greater body dissatisfaction. The present study aims to determine associations among adolescents’ (girls and boys) gender identity, loneliness, body dissatisfaction, and fear of negative appearance evaluation, as well as to examine the possible mediating roles of body dissatisfaction and fear of negative appearance evaluation between adolescents’ gender identity and loneliness, and how these phenomena differ for girls and boys. The sample consists of 211 adolescents in the 10th grade from five secondary public schools (gymnasiums) in Vilnius, Lithuania, 54.5 % of whom were girls and 45.5 % boys. Participants were between the ages of 15 and 17 (Mage = 16.20, SDage = 0.43). During the study, adolescents were asked to fill out self-reported questionnaires: gender identity was measured using the Gender Identity / Gender Dysphoria Questionnaire for Adolescents and Adults (GIDYQ-AA; Deogracias et al., 2007); subjective feelings of loneliness were measured using the UCLA Loneliness Scale (Russell, Peplau, & Ferguson, 1978); body dissatisfaction was measured using the Body Shape Questionnaire (BSQ; Dowson & Henderson, 2001); and the Fear of Negative Appearance Evaluation Scale (FNAES; Thomas et al., 1998; cited by Lundgren, Anderson, & Thompson, 2004) was used to measure apprehension regarding appearance evaluation. The processing and analysis of results was achieved using the IBM SPSS v.26.0 statistical package.First, comparative and correlation analysis was performed; second, the PROCESS v.4.1 for SPSS (Model 14) was used, and moderated mediation analysis was performed. The results of this study reveal that the gender identity of both girls and boys is negatively related to loneliness, body dissatisfaction, and fear of negative appearance evaluation. The results also show that the association between gender identity and loneliness is mediated by body dissatisfaction, and that the association between body dissatisfaction and loneliness is stronger for boys than for girls, but fear of negative appearance evaluation does not mediate the association between gender identity and loneliness. This study outlines the need to begin to pay more attention to the experiences of boys regarding body dissatisfaction and illustrates the importance of examining adolescents’ gender differences in body dissatisfaction, loneliness, and gender identity. Given the unique challenges that adolescents with gender identity issues face regarding body acceptance, they must have access to supportive environments and mental health resources that can assist them in their self-discovery, self-acceptance, and overall well-being, e.g., by reducing loneliness given the special obstacles that adolescents encounter around body acceptance. Thus, it is especially important to create inclusive and affirming environments that recognize and validate diverse gender identities. Keywords: adolescents, gender identity, loneliness, body dissatisfaction, fear of negative appearance evaluation. [From the publication]