Financial toxicity affects 30-50% of people with cancer in the US. Although experts recommend patients and physicians discuss treatment cost, cost discussions occur infrequently. We pilot-tested the feasibility, acceptability and influence on outcomes of the DIScussions of COst (DISCO) App, a multi-level communication intervention designed to improve cost discussions and related outcomes. While waiting to see their physician, patients (n=32) used the DISCO App on a tablet. Physicians were given a cost discussion tip sheet. Clinic visits were video recorded and patients completed pre- and post-intervention measures of self-efficacy for managing costs, self-efficacy for interacting with physicians, cost-related distress, and perceptions of the DISCO App. Coders observed the recordings to determine the presence of cost discussions, initiators, and topics. Most patients reported needing ≤15min to use the DISCO App, and that it made it easier to ask cost-related questions. Findings showed increased self-efficacy for managing treatment costs (p=.02) and for interacting with physicians (p=.001). All visits included a cost discussion. Prompting patients to discuss costs may improve cost treatment discussions and related outcomes. An app-based and tailorable treatment-cost communication intervention is feasible, acceptable, and demonstrates promise in prompting cost discussions and improving outcomes.Trial registration: Clinical Trials.gov registration number: NCT03676920 (September 19, 2018).