Social Networking Sites (SNSs) number at least 3.81 billion users worldwide, while in Greece, 74.7% of internet users resort to SNSs. However, there is no instrument adapted to the Greek language that assesses addiction to SNSs. The Bergen Social Media Addiction Scale is a short 6-item questionnaire that assesses social media addiction. This study aimed to evaluate the psychometric properties of the Greek version of the Bergen Social Media Addiction Scale. The sample consisted of 325 University students (mean age 21.6 years, SD=5.26). Confirmatory factor analysis was performed that supported the one-factor model. The reliability of the tool was tested with various indicators and was found to be satisfactory. The regression analysis identified gender, time of SNSs use, number of SNSs held by an individual and stress as statistically significant predictors of SNSs addiction. Positive correlations were found between SNSs addiction and stress, depression, anxiety and loneliness, while negative correlations were observed between SNSs addiction, self-esteem and age. Stress fully mediated the relationship between depression and SNSs addiction. The findings of the present study indicate that the Greek version of the Bergen Social Media Addiction Scale is a valid and reliable instrument for assessing SNSs addiction. The relationship between SNSs addiction and the biopsychosocial model was confirmed.