Rising child welfare costs and a desire to keep kids out of the system have encouraged the use of kinship care--of which custodial grandparents make up the majority of caregivers. Unfortunately, custodial grandparents report greater needs for social and emotional support to successfully care for their grandchildren. Yet, the resources required to provide preventive social-emotional support to these families are unknown. In the wake of the Family First Act and other policy actions to expand preventive services, we undertake a cost analysis of the social intelligence training (SIT) within a randomized controlled trial spanning 48 states of the United States of America. Estimated implementation costs were $90,638 (CI $45,254-186,998) which equated to $255 (CI $127-526) per participant. This dual-generation online approach offers key lessons into not only how to resource social-emotional learning (SEL) prevention for custodial grandparents--but also sheds light on how we might provide universal supports to this population. Child welfare system costs have risen to over $33 billion dollars a year--with nearly half of all spending being the result of out-of-home placement (Rosinsky et al., 2021) Child Welfare Financing SFY 2018: A survey of federal, state, and local expenditures. https://www.childtrends.org/wp-content/uploads/2021/05/ChildWelfareFinancing_ChildTrends_March2021.pdf). Practitioners, policymakers, and child advocates are seeking solutions for how to both better protect children and manage these growing public costs (Ringel et al., 2018). Improving child welfare outcomes: Balancing investments in prevention and treatment. Rand health quarterly, 7(4)). Further, many extended families seek ways to keep children out of the "system" when parents are unable to care for their offspring (Lin, Children and Youth Services Review 93:203-216, 2018). A strategy used by all of these groups is the use of kinship care arrangements where extended family provides formal or informal care of children. Several important benefits are recognized from kinship care, including providing connections to family members, communities, and culture. Yet, little is known about how social-emotional supports could enhance kinship arrangements, and to date, no studies have systematically evaluated the costs of such supports. In this context, we conduct a cost analysis of such a program--known as social intelligence training.