Excessive use of the Internet in recent years has caused different social problems. One of the most important consequences of excessive Internet usage is Internet addiction among students which directly affects their academic performance personal relationships with others, leading to social isolation. This study attempts to identify the relationships among gratification of using the Internet, Internet skill, Internet addiction, and social isolation among university students. In addition, the mediating role of Internet addiction between gratification of using the Internet and Internet skill with social isolation, and the role of race and gender were examined. A total of 440 university students in the age range of 18 to 40 years from the University of Putra Malaysia (UPM) participated in the study. Students completed a self-rank questionnaire measuring their Internet dependency. Structural Equation Modeling estimated that Internet addiction had moderating effects on gratification of using the Internet and social isolation. The moderation of race and gender on the model was not supported. In addition, females were more addicted and consequently more isolated from the society in comparison to males, though there were differences for Malay and non-Malay students.