Fostering participant engagement is a challenging but essential component of effective prevention programs. To better understand which factors influence engagement, this study examines several predictors of couple engagement in Family Foundations (FF), a preventive intervention for first-time parents shown to enhance parent mental health, couple relations, parenting quality, and child adjustment through age three years. FF consists of a series of classes delivered through childbirth education departments at local hospitals. Baseline data on socio-demographics, parent mental health, and couple relationship quality were examined as predictors of participants’ level of engagement in FF (n = 89 couples, 178 individuals). Sociodemographic variables such as parent gender, socioeconomic status, and age predicted program engagement to a limited extent. However, findings indicated that marital status was the best predictor of engagement. Discussion focuses on how findings can inform the development of practices that promote engagement, such as the use of targeted outreach efforts for individuals most at risk of disengagement.