Background and aims: Internet gaming disorder (IGD) has become a topic of increasing research interest since its inclusion in Section 3 of the DSM-5. Given the lack of clinical studies concerning IGD, exploring the characteristics of clinical samples with IGD will help to delineate the gaming disorder construct and inform future treatment studies. Methods: Data collection consisted of clinical interviews comprising 31 male adolescents diagnosed with IGD. Alongside the clinical interviews, the participants were administered a battery of psychometric tests assessing the following: IGD, personality traits, comorbid symptomatology, emotional intelligence (EI), and family environment characteristics. Results: The results showed that the adolescents with IGD and their relatives reported a high number of hours per week and high presence of stressful life events in the majority of the sample. High scores on scales assessing depression, anxiety, and somatic disorders were found. However, the findings indicate the presence of several other comorbid disorders meaning that some of the adolescent sample with IGD had different clinical profiles. Several personality traits were found to be highly associated with IGD including introversion, inhibition, submissiveness, self-devaluation, interpersonal sensibility, obsessive–compulsive tendencies, phobic anxiety, and hostility, as well as paranoid and borderline personality traits. Other negative characteristics found in the present sample included a high level of social problems, low EI, and dysfunctional family relationships. Discussion and conclusions: The findings suggest a more global pattern of key psychological characteristics associated with Internet gaming disorder in adolescence. This may help in understanding the complexity of this proposed disorder and it may also help in designing more specialized interventions for adolescents with IGD. The findings have important implications for clinical practice and interventions.