This study analysed "The 8th Online Survey of Adolescent Health and Behaviour in 2012", which is a government-approved statistical survey of Internet use and patterns in Korea. We conducted a propensity score matching (PSM) to control for economic status differences between monocultural and multicultural families and an ANOVA to estimate the effects of multicultural family status, adolescents' gender, school grades, locality, and parents' academic background on adolescents' Internet use (for studying and entertainment). The study revealed the following: with regard to Internet use patterns, adolescents from both monocultural and multicultural families selected gaming as their first choice, followed by studying and data searching. Furthermore, main and interaction effects of independent variables on adolescents' time spent on the Internet for studying were not significant. However, the interaction effects of multicultural family status and mothers' academic background on adolescents' time spent on the Internet for entertainment were statistically significant. Specifically, adolescents' time spent on the Internet for entertainment was higher in multicultural families with mothers whose education level was lower than middle school. Finally, we suggested that the government should provide full support to less educated mothers in multicultural families for effectively and constructively controlling their children's Internet use and teaching it to them.