The purpose of this study was to study the relationship between Internet addiction and academic performance among university undergraduates. The study also focused to examine the gender differences among students on internet addiction. The sample comprised of 359 university undergraduates. Their responses to the "Internet Addiction Scale" and GPA for the previous semester were collected and analyzed using methods including descriptive statistics, t-test, ANOVA, and simple linear regression analysis. The results suggested that internet addiction was a significantly negatively correlated with academic performance of university undergraduates. Results also suggested gender difference in internet addiction. Male students had higher internet addiction than female ones. Based on the above findings, some suggestions were proposed as a reference for practical applications and future research.