The study objective was to evaluate the association between depression, anxiety, social anxiety and fear, impulsivity, and aggression and Internet addiction (IA) among Lebanese adolescents. This cross-sectional study, conducted between October 2017 and April 2018, enrolled 1103 young adolescents aged between 13 and 17 years. The Internet Addiction Test (IAT) was used to screen for IA. The results also showed that 56.4% of the participants were average Internet users (IAT score ≤49), 40.0% had occasional/frequent problems (IAT scores between 50 and 79), and 3.6% had significant problems (IAT scores ≥80) because of Internet use. The results of a stepwise regression showed that higher levels of aggression (β = 0.185), depression (Multiscore Depression Inventory for Children) (β = 0.219), impulsivity (β = 0.344), and social fear (β = 0.084) were associated with higher IA, whereas an increased number of siblings (β = -0.779) and a higher socioeconomic status (β = -1.707) were associated with lower IA. Uncontrolled use of the Internet can be associated with addiction and other psychological comorbidities.