Videogame addiction has been suggested as a tentative disorder in 2013 by the American Psychiatric Association (APA) and was recently officially recognized as a mental health disorder by the World Health Organization (WHO). Although a few studies have identified attention deficit and hyperactivity disorder (ADHD) as a key risk factor for Internet Gaming Disorder (IGD), the interplay between ADHD and IGD symptoms with gender differences across cultures remains to be further examined.This study examined the moderating effects of gender in the association between ADHD and IGD across two nations.A cross-sectional online survey was developed to recruit 164 Australian (M = 23.01,  = 3.35, Min = 18, Max = 31, Males  = 121, 73.80%) and 457 U.S.-North American (M = 25.25 years,  = 2.76, Min = 18 years, Max = 29 years, Males = 265, 57.98%) Massively Multiplayer Online (MMO) players aged between 18 and 29 years.The hierarchical linear regression, moderation and moderated moderation analyses revealed that participants presenting greater inattention and hyperactivity symptoms exhibited higher levels of IGD-related behaviors in the two samples. Moreover, these associations differed across genders between the two countries. Specifically, more hyperactive-impulsive, as well as inattentive males in the USA presented higher levels of disordered gaming.The results highlight the need for more cross-cultural and symptom-focused research in the broader IGD field.