Abstract The association between traumatic experiences, alexithymia, and substance abuse is well established. Less is known about the role of traumatic experiences and alexithymia in the onset and maintenance of Internet-related disorders. In the present study, self-report measures on traumatic experiences, alexithymia, and problematic Internet use were administered to 358 high school students (57% females) aged 18–19 years old, to test whether alexithymic traits mediated the relationship between traumatic experiences and Internet addiction symptoms, and whether gender moderated the proposed mediation in the sample. While partial mediation occurred in the entire sample, gender directly affected the relationship between the investigated constructs: Internet addiction symptoms were independently related to traumatic experiences among males, and to alexithymic traits among females. Therefore, the results of this study suggest that trauma memories among males, and problems with affect regulation among females, may increase the risk of problematic Internet use during late adolescence. Such findings might have relevant implications to inform any treatment plan for late adolescent students who are overinvolved with online activities, pointing out that tailored approaches to their problems and difficulties are particularly needed in clinical practice.