Objectives: Hip osteoarthritis and knee osteoarthritis cause significant disability and pain in older adults, often leading to hip or knee replacement surgery. Prehabilitation programs have been established for these surgeries, but there are few programs for orthogeriatrics. We evaluated the feasibility of a new multimodal prehabilitation program (MPP) for older adults before hip or knee replacement due to arthrosis: the Prehabilitation for Os (PRE4OS) study. Design: We conducted a multicenter feasibility study in the Greater Paris area. Setting and participants: Eligible adults were ≥75 years old awaiting hip or knee replacement with at least a 6-week delay before surgery and able to participate in the MPP follow-up. The MPP included weekly hospital sessions providing nutritional, psychological, functional, and cognitive support, along with weekly home sessions featuring physiotherapist visits. Methods: The primary outcome was at least 80% of 1-day hospital (ODH) sessions performed by 80% of participants. Secondary outcomes included intervention achievement, quality of life, and nutritional and functional status changes. Participant's satisfaction was qualitatively assessed via structured phone interviews presurgery and at 30 days postsurgery. Results: From September 2021 to September 2023, a total of 27 individuals participated in the PRE4OS study. The mean (SD) age was 83 (4.3) years, with 7 males (26%) and median baseline Activities of Daily Living score 5.5 (interquartile range 5.5-6.0). Surgeries were for insertion of hip prosthesis in 17 participants (63%) and knee prosthesis in 10 (37%). The primary outcome was achieved in 89% of participants, with comparable rates for hip and knee prostheses. In total, 60% of participants rated the MPP as "excellent" presurgery and 100% at 30 days postsurgery, expressing a willingness to recommend the protocol to a friend or family. Conclusion and implications: The MPP was feasible for individuals before hip or knee replacement and was well received. Further randomized trials are needed to assess its clinical impact.