The purpose of this study is to examine how well university students' social anxiety, happiness and loneliness levels explain their levels of social media addiction. The research was designed as a correlational survey model. The research group consisted a total of 312 university students, 165 female (53%) and 147 male (47%), attending at a state university in Turkey during the 2017-2018 academic year. The data collected using a Personal Information Form, a Social Media Addiction Scale, a Social Anxiety Scale, the short form of the Oxford Happiness Questionnaire, and the short form of the UCLA Loneliness Questionnaire. Pearson correlation and hierarchical regression analysis were conducted in SPSS to investigate the relationship between students' social media addiction and their social anxiety, happiness, and loneliness levels. The findings showed that there was a positive relationship between students' social media addiction levels and their social anxiety and loneliness levels. On the other hand, there was a negative relationship between students' social media addiction levels and their happiness levels. According to these findings, social media addiction variable significantly predicted by the social anxiety and happiness variables, but it did not significantly predicted by the loneliness variable. The findings were discussed in the light of the relevant literature and recommendations were presented.