Passive Facebook use, which involves engaging in non-socially orientated behavior on the popular social networking site, is associated with a range of negative outcomes, including social anxiety, loneliness, jealousy, and depressed mood. Research indicates that passive Facebook use may also be related to a tendency to engage in social comparison with others. In addition, there is some evidence that this tendency is more prevalent in individuals high in the personality trait neuroticism. The aim of this study was to investigate the relationships between passive Facebook use, neuroticism, and social comparison orientation (SCO). In addition, we explored whether SCO mediates the potential relationship between neuroticism and passive Facebook use. In a cross-sectional study, 318 Estonian Facebook users completed the Multidimensional Scale of Facebook Use (to ascertain passive Facebook use), the Extra Short Big Five Personality Inventory, and the Iowa-Netherlands Comparison Orientation Scale. The results revealed positive bivariate-correlations between passive Facebook use, neuroticism, and SCO. In addition, SCO mediated the relationship between neuroticism and passive Facebook use. These findings suggest that people higher in neuroticism are more prone to social comparison, which is associated with passive Facebook use. These findings are discussed, and several directions for future research are provided.