Background: Physical activity (PA) decreases during hospitalization. In particular, the amount of PA engaged in by older people who are hospitalized following musculoskeletal injury is likely to be limited for months after discharge home. Given the importance of an active lifestyle for their recovery and the prevention of future adverse outcomes, there is clearly a need for interventions to increase PA. This article describes the protocol of a randomized controlled trial set up to investigate the effects of a physical activity oriented home rehabilitation program (ProPA) on PA and the restoration of mobility in community-dwelling older people. Methods: Men and women aged 60 years or older hospitalized due to a musculoskeletal injury or disorder in the back or lower limbs are recruited. After discharge from hospital to home, participants are randomized into a six-month ProPA program or a standard care (control) group. The ProPA program consists of a motivational interview, goal attainment process, guidance for safe walking, a progressive home exercise program and physical activity counseling. In addition, frail participants who are not able to go outdoors alone receive support from volunteers. Primary outcomes are PA measured using a 3-dimentional accelerometer, and mobility assessed by the Short Physical Performance Battery and self-reports. Secondary outcomes are life space mobility, participation restriction, fear of falling, pain, mood, and grip strength. Information on barriers to and enablers of PA participation are also collected. Data on mortality and use of health services are collected from the national register. In this 6-month intervention, all participants are assessed in their homes at baseline and after three and six months, and at 12 months after randomization they will receive a follow-up questionnaire. Discussion: This study investigates the effects of a rehabilitation program on PA and mobility among older people at risk for increased sedentary time and mobility problems. If positive effects are observed, the program can be considered for incorporation into the health care system and thereby contribute to the rehabilitation of older people who have recently been discharged from hospital.