The purpose of this study was to examine the levels of Internet addiction and interpersonal problems, explore the relationship between the two, and identify the relevant factors of Internet addiction in Korean middle school students. A cross-sectional survey design was used. The participants were 676 middle school students. A Korean version of the Internet addiction self-test scale and a Korean version of the Inventory of Interpersonal Problems were used. Among the participants, 547 (80.9%) were identified as general users, 108 (16%) were potential risk users, and 21 (3.1%) were high-risk users. There were statistically significant positive correlations between Internet addiction and interpersonal problems (r = 0.425, P = .000). There were significant positive correlations between Internet addiction and hours spent playing games. Internet-addicted adolescents also had more interpersonal problems. It is important to raise awareness about Internet addiction, and close attention must be paid not only to students at risk of Internet addiction but also to students at low risk to prevent students from becoming addicted to the Internet.