The current study investigated the relationship between problematic Internet use and social interaction anxiety among pre-service teachers. Participants were 1235 students attending teacher training programs at a Turkish state university. The "Problematic Internet Use Scale" and "Social Interaction Anxiety Scale" were used to collect the data. Independent-samples t-test and one-way ANOVA were conducted to examine the differences; and correlation and regression analyses were used to examine the relationships between variables. Findings revealed that male students' use of the Internet was more problematic compared to female students'. As the time spent on the Internet increased, so did the problematic Internet use levels. In addition, the problematic Internet use levels of students varied with regard to departments. A significant relationship was found between the level of problematic Internet use and social interaction anxiety, and social interaction anxiety was found to be among the predictors of problematic Internet use. Implications and suggestions for further research are provided. (Contains 8 tables and 1 figure.)