Lack of activity during hospitalization may contribute to functional decline. The purpose of this study was to investigate (1) the time spent walking during hospitalization by geriatric patients referred to physical and/or occupational therapy and (2) the development in time spent walking during hospitalization. In this observational study, 24-hr accelerometer data (ActivPal) were collected from inclusion to discharge in 124 patients at an acute geriatric ward. The median time spent walking was 7 min per day. During the first quartile of hospitalization, the patients spent 4 (IQR:1;11) min per day walking, increasing to 10 (IQR:1;29) min during the last quartile. Improvement in time spent walking was primarily observed in the group able to perform the Timed Up & Go task at admission. When walking only 7 min per day, patients could be classified as inactive and at risk for functional decline; nonetheless, the physical activity level increased significantly during hospitalization.