The extent to which evidence-based practices (EBPs) are considered cost-effective influences educators' adoption decisions. However, what it means to be cost-effective and how to interpret cost-effectiveness ratios may be unclear. This systematic review of cost-effectiveness analyses of EBPs in schools illuminates the many sources of variability in published estimates. Studies were limited to peer-reviewed, school-based studies conducted in the United States between 2000 and 2020. Seven studies examining eight programs were identified and then coded for program descriptions, outcomes, research designs, and cost-effectiveness methodology. Secondary analyses illustrated how published estimates can be adjusted to reduce methodological variability and increase the utility of comparisons. The small number of studies highlights the need for research to evaluate the cost-effectiveness of more EBPs. Implications for research and practice are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).