Objective Australian weekend rehabilitation therapy provision is increasing. Staff engagement optimises service delivery. The present mixed-methods process evaluation explored staff perceptions regarding implementation of a 6-day physiotherapy service in a private rehabilitation unit. Methods All multidisciplinary staff working in the rehabilitation unit were surveyed regarding barriers, facilitators and perceptions of the effect of a 6-day physiotherapy service on length of stay (LOS) and patient goal attainment at three time points: before and after implementation, as well as after modification of a 6-day physiotherapy service. Descriptive statistics and thematic analysis was used to analyse the data. Results Fifty-one staff (50%) responded. Before implementation, all staff identified barriers, the most common being staffing (62%) and patient selection (29%). After implementation, only 30% of staff identified barriers, which differed to those identified before implementation, and included staff rostering and experience (20%), timing of therapy (10%) and increasing the allocation of patients (5%). Over time, staff perceptions changed from being unsure to being positive about the effect of the 6-day service on LOS and patient goal attainment. Conclusion Staff perceived a large number of barriers before implementation of a 6-day rehabilitation service, but these did not eventuate following implementation. Staff perceived improved LOS and patient goal attainment after implementation of a 6-day rehabilitation service incorporating staff feedback. What is known about this topic? Rehabilitation weekend services improve patient quality of life and functional independence while reducing LOS. What does this study add? Staff feedback during implementation and modification of new services is important to address potential barriers and ensure staff satisfaction and support. What are the implications for practitioners? Staff engagement and open communication are important to successfully implement a new service in rehabilitation.