(1) Background: Bullying victimization has been associated with several behavioral outcomes, particularly loneliness. Similarly, an increase in social network use has been identified in recent years, particularly during the COVID-19 pandemic, and has been shown to be associated with bullying and loneliness. Investigating the mediating factors of loneliness among bullied adolescents is useful for taking preventive measures in the Lebanese population. This study aims to examine the association between bullying victimization and loneliness among Lebanese adolescents while considering the indirect effect of problematic social network use. (2) Methods: We carried out a cross-sectional study, between January and April 2022, that enrolled 379 adolescent Lebanese students (64.9% females, mean age 16.07 ± 1.19 years) who were current residents of Lebanon (15 to 18 years), and were from the five governorates of Lebanon (Beirut, Mount Lebanon, North, South and Bekaa). The snowball method was applied to select our sample; an electronic copy of the questionnaire was created using the Google Forms software and an online strategy was designed to collect the data. (3) Results: Negative social comparison and addictive consequences of problematic use of social network mediated the association between bullying victimization and loneliness. Higher bullying victimization was significantly associated with higher negative social comparison and addictive consequences of problematic use of social network, which in turn were significantly associated with more loneliness. Finally, higher bullying victimization was directly significantly associated with more loneliness. (4) Conclusions: Studying the mediating factors of loneliness in bullied adolescents can improve our understanding of this topic, allowing us to propose new interventions to prevent psychological problems in adolescents. Future studies are needed to further clarify the physiological processes that underlie the associations between social triggers and loneliness during adolescence.