Background: Children’s behavioral problems have high prevalence among families in the child welfare system, raising the need for cost-effective ways to diminish the problems.

Objective: We evaluated the cost-effectiveness of the Incredible Years® (IY) Parenting Program for children’s behavioral problems compared with a treatment-as-usual (TAU) in families receiving child protection services (CPS) and other family support services in Finland, from the health and social care payer’s perspective at the intervention end (post-assessment) and with a 12-month follow-up. Participants and setting: The randomized controlled trial included 102 families of 3–7-year-olds with behavioral problems. Families were recruited from CPS and other family support services in Finland.

Methods: Incremental net monetary benefit analysis combined the costs and effects of IY intervention and TAU groups. Costs included intervention costs and register-based children’s and mothers’ health and social care costs. Effectiveness measures were the Eyberg Child Behavior Inventory and the Child Behavior Checklist.

Results: In the post-assessment, the cost-effectiveness results varied according to the effectiveness measures. Compared to TAU, the IY intervention was either not cost-effective or the cost-effectiveness depended on the decision-makers’ willingness to pay. In the 12-month follow-up, IY and TAU did not differ in costs or effects. Conclusions: The cost-effectiveness estimates from previously studied populations may not generalize to families receiving CPS. Families receiving CPS are in urgent need of cost-effective support to reduce the high prevalence of children’s behavioral problems. Keywords: cost-effectiveness, parenting program, behavioral problems, child protection services, social services.