Background: While recent studies suggest a high prevalence of Internet gaming disorder (IGD) in child and adolescent psychiatry (CAP) clinics, little is known about the factors contributing to problematic gaming among these patients. Given the well-established role of parenting and parent-child relationships in the development of problem behaviors, this study aimed to explore parent-child relationships within a Swedish cohort of CAP patients with IGD. Methods: A total of 72 adolescents from CAP clinics in Skane, Sweden, diagnosed with IGD based on DSM-V criteria (73% boys), aged 13 to 18 years were included in the study. The adolescents completed the Game Addiction Scale for Adolescents (GASA) and reported on aspects of parent-child communication, such as parental control and adolescent disclosure and secrecy, and family climate. Adolescents were categorized as engaged, problem or addicted gamers based on core approach. Independent sample t-tests, Pearsons’s correlations, and multivariate regression analyses were used to address the study goals. Results: Independent sample t-tests revealed that girls showed lower levels of parental knowledge than boys. Bivariate correlation analyses showed that IGD-symptoms were related to lower levels of child disclosure, while multivariate regression analyses revealed that higher IGD-symptoms were predicted by high levels of child secrecy and low child disclosure. Conclusion: Parent-child relationships, in particular adolescent information management to parents, plays an important role for the level of IGD-symptoms in a clinical sample of adolescents. We suggest that therapeutic interventions for IGD should integrate family-focused strategies, such as parent training programs fostering open communication between parents and their children.