We conducted a study to evaluate the effectiveness of Mom Power, a multifamily parenting intervention to improve mental health and parenting among high-risk mothers with young children in a community-based randomized controlled trial (CB-RCT) design. Participants (N = 122) were high-risk mothers (e.g., interpersonal trauma histories, mental health problems, poverty) and their young children (age <6 years), randomized either to Mom Power, a parenting intervention (treatment condition), or weekly mailings of parenting information (control condition). In this study, the 13-session intervention was delivered by community clinicians trained to fidelity. Pre- and post-trial assessments included mothers’ mental health symptoms, parenting stress and helplessness, and connection to care. Mom Power was delivered in the community with fidelity and had good uptake (>65%) despite the risk nature of the sample. Overall, we found improvements in mental health and parenting stress for Mom Power participants but not for controls; in contrast, control mothers increased in parent-child role reversal across the trial period. The benefits of Mom Power treatment (vs. control) were accentuated for mothers with interpersonal trauma histories. Results of this CB-RCT confirm the effectiveness of Mom Power for improving mental health and parenting outcomes for high-risk, trauma-exposed women with young children.