Older adults (people aged 65 years and older) face many difficult decisions. Patient decision aids (PtDAs) can help them and their families make informed value-congruent decisions. Some PtDAs have been developed for the home care context, but little is known about scaling them for use with older adults in a different culture. This study aims to (1) assess the scalability of existing PtDAs for older adults in the home care context; (2) prioritize those that best match the decisional needs of older adults in home care; and (3) culturally adapt the prioritized PtDAs so they can be scaled successfully to the Quebec health care system. This multimethod study includes 3 phases. All phases will be overseen by a steering committee of older adults, caregivers, health professionals, decision makers, community organization representatives, and researchers with the needed expertise. In phase 1, we will use the Innovation Scalability Self-administered Questionnaire, a validated scalability self-assessment tool, to assess the scalability of 33 PtDAs previously identified in a systematic review. Based on their scalability, their quality (based on the International Patient Decision Aids Standards), and the importance of the decision point, we will retain approximately a third of these. In phase 2, we will conduct a 2-round web-based Delphi to prioritize the PtDAs selected in phase 1. Using a snowball recruitment strategy, we aim to recruit 60 Delphi participants in the province of Quebec, including older adults, caregivers, health professionals, decision makers involved in home care services, and PtDA experts. In the first round, we will ask participants to rate the importance of several PtDA decision points according to various criteria such as prevalence and difficulty on a 5-point Likert scale (1=not important to 5=very important). Approximately 6 of the highest-rated PtDAs will be retained for presentation in the second round, and we will select up to 3 PtDAs judged as having the highest priority for cultural adaptation. In phase 3, using the Chenel framework and user-centered design methods, we will update and adapt the PtDAs to the Quebec health care system and integrate these PtDAs into an interprofessional shared decision-making training program for home care teams. The adapted PtDAs will respect the International Patient Decision Aids Standards criteria. This study was funded in March 2022 by the Canadian Institutes of Health Research. Data collection for the web-based Delphi began in October 2023. Results are expected to be published in May 2024. This project will provide relevant and culturally appropriate decision support tools for older adults making difficult decisions and their home care teams that will be ready for scaling across the province of Quebec. PRR1-10.2196/53150.