Background: After diagnosis, adults with Stage III non-small cell lung cancer (NSCLC) face an overwhelming range of decisions, many of which are preference-sensitive. Patients often report poor communication with their clinicians, including limited discussion and consideration of their treatment preferences. As such, we developed the Preparation for Shared Decision-Making (PFSDM) tool to improve patient experience and engagement with clinicians when conducting treatment discussions. The study objective was to validate the PFSDM tool for acceptability and usability among patients with Stage III NSCLC. Methods: We used a recruitment service to identify interviewees, and conducted 20 one-on-one, semi-structured interviews with adults diagnosed with Stage III NSCLC. Interview questions were designed to elicit feedback on patients’ perceptions of the tool’s acceptability and usability using eight themes: understandability, clarity of information, amount of information, suitability for decision making, usefulness, relevance of information, value, and formatting. We used template analysis to code transcripts, using 19 codes decided a priori, allowing for additional codes to emerge. Two interviewers double coded 4 interviews, ensuring interrater reliability >75% and reconciled differences, subsequently independently coding the remaining interviews (n=16). Results: Of the 20 interviewees, 13 (65%) were female, 12 (60%) 55-64 years old, 18 (90%) identified as white, 16 (80%) had less than college degree, and 9 (45%) reported less than $50,000 household income over past 12 months. Overall, we found patients reported positive acceptability and usability, with positive statements about the tool across all 8 themes and 1 emergent sub-theme (overall usefulness). Across 20 interviews, where discussed, there were 18 positive and 0 negative statements about overall understanding, indicating high acceptability, and 16 positive and 0 negative statements about overall usefulness, indicating high usability among this sample. Conclusion: Results suggest patients with Stage III NSCLC find the PFSDM tool acceptable and usable. Findings indicate patients believe the tool will help them prepare to communicate their preferences with their provider when making decisions. Results will be used to update the tool with patient recommendations and inform future studies evaluating the feasibility of incorporating the tool into the clinical workflow and the tool’s impact on clinical outcomes.