This study investigated whether the amount and circadian time of habitual computer game playing were related to depressive symptoms in adolescents and young adults. We expected that habitual late playing relates to more depressive symptoms beyond the effect of the total time of computer game playing as playing at night may involve short, irregular, and disturbed sleep as well as misalignment of the circadian rhythm. 646 adolescents and young adults (ages 13–30; 90.9% males) who play the internet role-playing game World of Warcraft completed an online questionnaire. Habitual computer game playing between 10 pm and 6 am was related to an increased risk of high depression scores independent of the total amount of playing. Adolescents (ages 13–17 years) were most vulnerable when habitually playing during early night (i.e., 10–12 pm), while emergent adults (ages 18–22 years) showed more vulnerability when habitually playing late at night (i.e., after 2 am). The effect was partly mediated by daytime sleepiness but not by sleep loss or insomnia problems.