Online social networking sites, such as Facebook, have provided a new platform for individuals to produce and reproduce gender through social interactions. New mothers, in particular, may use Facebook to practice behaviors that align with their mothering identity and meet broader societal expectations, or in other words, to "do motherhood." Given that Facebook use may undermine well-being, it is important to understand the individual differences underlying new mothers' experiences with Facebook during the stressful first months of parenthood. Using survey data from a sample of 127 new mothers with Facebook accounts residing in the U.S. Midwest, we addressed two key questions: (a) Are individual differences in new mothers' psychological characteristics associated with their use and experiences of Facebook? and (b) Are new mothers' psychological characteristics associated with greater risk for depressive symptoms via their use and experiences of Facebook? Regression analyses revealed that mothers who were more concerned with external validation of their identities as mothers and those who believed that society holds them to excessively high standards for parenting engaged in more frequent Facebook activity and also reported stronger emotional reactions to Facebook commentary. Moreover, mothers who were more concerned with external validation were more likely to have featured their child in their Facebook profile picture. Mediation analyses indicated that mothers who were more prone to seeking external validation for their mothering identity and perfectionistic about parenting experienced increases in depressive symptoms indirectly via greater Facebook activity.