question: BACKGROUND Shared decision-making (SDM) involves patients and clinicians choosing treatment jointly. SDM in mental health is hampered by lack of well-developed supporting tools. We describe an evidence-based patient decision aid (PDA) to facilitate SDM for treatment-resistant depression (TRD) following US National Quality Forum standards which are based upon the International Patient Decision Aid Standards (IPDAS). METHODS A web-based PDA was developed by a multidisciplinary steering committee of clinicians, patient advocates, patients and a decision scientist. Development included creating content consistent with decision-making domains that are impacted by patient preference in TRD. Development was guided by literature review, group conference calls/discussions, patient and clinician interviews (N = 8), high and lower literacy focus groups (N = 11) and pilot study (N = 5). The PDA presents risk-benefit information on domains (e.g., effectiveness, mode of administration, side effects, cost) and includes values clarification exercises. Pilot study patients were administered the Decisional Conflict Scale (DCS) and Decision Self-Efficacy Scale (DSES) prior to and following PDA interaction and clinician SDM. RESULTS During the pilot, prior to PDA interaction, mean (standard deviation) DCS score was 42.2 (14.4) and DSES score was 86.0 (14.6) out of 100. Following PDA interaction and SDM, DCS decreased (improved) to 28.1 (SD 4.1) and DSES increased to 95.5 (6.7). All patients endorsed that the PDA helped them to: recognize pros and cons of options; understand how treatments were administered, possible side-effects, and likelihood of benefit; recognize what was important relative to the decision; organize thoughts and prepare for a discussion with their clinician. CONCLUSIONS This PDA may support SDM in TRD. A future trial to determine impact of the present SMD on decision-making quality is warranted. It also highlights gaps in comparative effectiveness trials that could guide equitable shared decision-making.