Background: To reduce adverse outcomes of low hospital mobility, we need interventions that are scalable in everyday practice. This study assessed the feasibility and acceptability of the INTOMOB multilevel intervention addressing barriers to hospital mobility without requiring unavailable resources. Methods: The INTOMOB intervention, targeting older patients, healthcare professionals (HCPs) and the hospital environment, was implemented on acute general internal medicine wards of three hospitals (12/2022-03/2023). Feasibility and acceptability of the intervention were assessed and two types of accelerometers compared in a mixed methods study (patient and HCP surveys and interviews). Quantitative data were analyzed descriptively and qualitative data using a deductive approach. Results were integrated through meta-inferences. Results: Of 20 patients (mean age 74.1 years), 90% found the intervention helpful and 82% said the environment intervention (posters) stimulated mobility. The majority of 44 HCPs described the intervention as clear and helpful. There was no major implementation or technical issue. About 60% of patients and HCPs preferred a wrist-worn over an ankle-worn accelerometer. Conclusions: The INTOMOB intervention is feasible and well accepted. Patients' and HCPs' feedback allowed to further improve the intervention that will be tested in a cluster randomized trial and provides useful information for future mobility-fostering interventions.