Introduction: This study determines if expenditures associated with implementing a combined motivational interviewing (MI) and Head Start-level education program (MI+Education), as compared to education alone, yield cost savings to society. Methods: Post hoc cost analyses were applied to a randomized controlled-trial of MI among predominantly African American, low-income caregivers of 330 Baltimore City Head Start students who reside with a smoker. The primary outcome was the cost savings of MI+Education from averted direct secondhand smoke exposure (SHSe)-related acute healthcare events and inferred indirect costs (work days lost, transportation and reduction in cigarettes smoked). The net direction of savings was defined by the sum of averted direct and indirect costs of the MI+Education intervention at 3, 6 and 12 months, benchmarked against the Education alone cohort at the equivalent time periods. Results: The costs saved by the MI+Education intervention, relative to Education alone, resulted in savings at solely the 12-month follow-up time point. Significant savings were appreciated from averted emergency department (ED) visits at 12 months ($4410; 95% simulation interval [SI]: $2241, $6626) for the MI+Education group. The total savings at 12 months ($2274; 95% SI: -3916, $8442) could not overcome additional program costs of implementing MI to Head Start-level education ($13 695; 95% SI: $11 250, $16 034). Conclusions: This study is the first to examine the cost of either intervention on SHSe-attributed pediatric healthcare costs from a population level relevant for federal and community decision makers. Intervention costs could not be offset by short-term savings but a trend towards positive savings was appreciated 1 year after implementation. Implications: Behavioral interventions are effective in reducing SHSe in children. However, many of these interventions are not implemented in community settings due to lack of resources and money. Behavioral strategies may be a cost-saving addition to the national initiatives to create smoke-free home environments. The long-term benefits of MI, as evidenced from cost savings from averted ED visits, appeared to show MI+Education to be a robust long-term strategy. The decrease of acute healthcare services at 12 months may be informative for policy decision makers seeking to allocate limited resources to reduce the usage of costly ED services and hospital readmissions. (author abstract)