A cross-sectional descriptive study research design was employed to investigate the prevalence of internet addiction and to explore the relationship among internet addiction, stress and academic outcome of undergraduate students of a private international university in Thailand. Data was collected through the distribution of 400 questionnaires to undergraduate students of a private international university between January and February 2011. The set of questionnaires consisted of data including academic outcome, Self-Internet Addiction Test (SIAT), and Health Opinion Survey (HOS). Convenience sampling was used to obtain potential subjects.