Background: Gaming Disorder (GD) was recently included by the World Health Organization (WHO) as a psychiatric condition in the eleventh revision of the International Classification of Diseases (ICD-11) and is a concern worldwide, including in Iran. Thus, based on the ICD-11 criteria, a Persian version of the Gaming Disorder Test (GDT) was developed to facilitate assessment of GD. Methods: The present study used classical test theory and Rasch analysis to examine the psychometric properties of the Persian GDT. Iranian adolescents (n = 3837; 2171 [56.6%] males; mean [SD] age = 16.02 [1.4] years) completed the GDT and other instruments assessing disordered gaming, psychological distress, and insomnia. Results: Overall, the psychometric properties of the Persian GDT were satisfactory based on classical test theory (i.e., confirmatory factor analysis corroborated the unidimensional structure of GDT) and Rasch analysis (i.e., fit statistics suggested that all items were embedded in the concept of GD). Moreover, the Persian GDT was found to be sex-invariant, displaying no items with substantial differential item functioning across sexes. Additionally, it was found that GD mediated associations between time spent gaming and measures of psychological distress and insomnia. Conclusion: The Persian GDT is a convenient and short instrument for assessing GD among Iranian adolescents. The mediating roles of GD in the associations between time spent gaming and psychological distress and between time spent gaming and insomnia suggest that targeting features of GD may reduce psychological distress and improve sleep for Iranian adolescents.