The aim of this study is to investigate the relationships between attachment characteristics, alexithymia and problematic internet use (PIU) in adolescents. The study was performed on 444 high school students (66% female and 34% male). Internet Addiction Test (IAT), Toronto Alexithymia Scale (TAS-20) and Short Form of the Inventory of Parent and Peer Attachment (s-IPPA) scales were used. The adolescents who scored 50 on IAT were considered as the PIU group and <50 were considered as control group. There was a moderate positive relationship between TAS-20 and IAT scores (r=.441), and a moderate negative relationship between TAS-20 and s-IPPA scores (r=-.392), and a negative weak relationship between IAT and s-IPPA scores (r=-.208). S-IPPA scores were significantly lower in the PIU group compared to the controls (p<.001). TAS-20 scores of the PIU group were significantly higher compared to the controls (p<.05). Logistic regression analysis indicated that s-IPPA scores and TAS-20 significantly predict the PIU development (p<.05). The results indicate that alexithymia increases the risk of PIU and higher attachment quality is a protective factor for both alexithymia and PIU. These results suggest that it is important to focus on the insecure attachment patterns and alexithymic characteristics when studying adolescents with PIU.