This study examined the relationship between social media addiction and depression among students of the universities in Khost province of Afghanistan. Stratified random sampling was used and a 46-items selfadministered questionnaire was distributed to 384 students of three universities Shaikh Zayed, Ahmad Shah Abdali, and Pamir University. Kimberly Young's Internet Addiction Test (IAT) was applied and replicated for measuring social media addiction; depression was measured by the Centre for Epidemiologic Studies Depression Scale (CES-D). The Pearson correlation coefficient, simple linear regression and factor analysis were employed to determine the relationship between social media addiction and depression. The findings indicated that social media addiction has a positive correlation with depression and depression significantly predicts social media addiction.