Background Sustained delivery of evidence-based treatments (EBTs) is essential to addressing the public health impacts of youth mental health problems, but is complicated by the limited and fragmented funding available to youth mental health service agencies. Supports are needed that can guide service agencies in accessing sustainable funding for EBTs. We conducted a pilot evaluation of the Fiscal Mapping Process, an Excel-based strategic planning tool that helps service agency leaders identify and coordinate financing strategies for their EBT programs. Method Pilot testing of the Fiscal Mapping Process was completed with 10 youth mental health service agencies over a 12-month period, using trauma-focused cognitive-behavioral therapy or parent–child interaction therapy programs. Service agency representatives received initial training and monthly coaching in using the tool. We used case study methods to synthesize all available data (surveys, focus groups, coaching notes, document review) and contrast agency experiences to identify key findings through explanation building. Results Key evaluation findings related to the process and outcomes of using the Fiscal Mapping Process, as well as contextual influences. Process evaluation findings helped clarify the primary use case for the tool and identified the importance—and challenges—of engaging external collaborators. Outcome evaluation findings documented the impacts of the Fiscal Mapping Process on agency-reported sustainment capacities (strategic planning, funding stability), which fully explained reported improvements in outcomes (extent and likelihood)—although these impacts were incremental. Findings on contextual factors documented the influence of environmental and organizational capacities on engagement with the tool and concerns about equitable impacts, but also the view that the process could usefully generalize to other EBTs. Conclusions Our pilot evaluation of the Fiscal Mapping Process was promising. In future work, we plan to integrate the tool into EBT implementation initiatives and test its impact on long-term sustainment outcomes across various EBTs, while increasing attention to equity considerations.