Background and aims The latest (fifth) edition of the Diagnostic and Statistical Manual of Mental Disorders included Internet gaming disorder (IGD) as a disorder that needs further research among different general populations. In line with this recommendation, the primary objective of this was to explore the relationships between IGD, sleep habits, and academic achievement in Lebanese adolescents. Methods Lebanese high-school students (N = 524, 47.9% males) participated in a paper survey that included the Internet Gaming Disorder Test and demographic information. The sample's mean average age was 16.2 years (SD = 1.0). Results The pooled prevalence of IGD was 9.2% in the sample. A hierarchical multiple regression analysis demonstrated that IGD was associated with being younger, lesser sleep, and lower academic achievement. While more casual online gamers also played offline, all the gamers with IGD reported playing online only. Those with IGD slept significantly less hours per night (5 hr) compared with casual online gamers (7 hr). The school grade average of gamers with IGD was the lowest among all groups of gamers, and below the passing school grade average. Conclusions These findings shed light on sleep disturbances and poor academic achievement in relation to Lebanese adolescents identified with IGD. Students who are not performing well at schools should be monitored for their IGD when assessing the different factors behind their low academic performance.