OBJECTIVES: To test effects of a social media-based parenting program for mothers with postpartum depressive symptoms. METHODS: We conducted a randomized controlled trial from December 2019 to August 2021 of a parenting program using Facebook. Women with mild-to-moderate depressive symptoms (Edinburgh Postnatal Depression Scale [EPDS] 10–19) were randomized to the program, plus online depression treatment or depression treatment alone for 3 months. Women completed the EPDS monthly and the Parent–Child Early Relational Assessment, Parenting Stress Index-Short Form, and Parenting Sense of Competence pre- and postintervention. Differences among groups were assessed using intention-to-treat analysis. RESULTS: Seventy-five women enrolled and 66 (88%) completed the study. Participants were predominantly Black (69%), single (57%), with incomes <$55 000 (68%). The parenting group reported a more rapid decline in depressive symptoms than the comparison group (adjusted EPDS difference, −2.9; 95% confidence interval, −4.8 to −1.0 at 1 month). There were no significant group X time interactions for the Parent–Child Early Relational Assessment, Parenting Stress Index-Short Form, or Parenting Sense of Competence scores. Forty-one percent of women sought mental health treatment for worsening symptoms or suicidality. Women in the parenting group who exhibited greater engagement or reported mental health treatment had greater parenting responsiveness. CONCLUSIONS: A social media-based parenting program led to more rapid declines in depressive symptoms but no differences in responsive parenting, parenting stress, or parenting competence relative to a comparison group. Social media can provide parenting support for women with postpartum depressive symptoms, but greater attention to engagement and treatment access are needed to improve parenting outcomes.