To evaluate the construct validity and the inter-rater reliability of the Dutch Activity Measure for Post-Acute Care “6-clicks” Basic Mobility short form measuring the patient’s mobility in Dutch hospital care. First, the “6-clicks” was translated by using a forward-backward translation protocol. Next, 64 patients were assessed by the physiotherapist to determine the validity while being admitted to the Internal Medicine wards of a university medical center. Six hypotheses were tested regarding the construct “mobility” which showed that: Better “6-clicks” scores were related to less restrictive pre-admission living situations (p = 0.011), less restrictive discharge locations (p = 0.001), more independence in activities of daily living (p = 0.001) and less physiotherapy visits (p < 0.001). A correlation was found between the “6-clicks” and length of stay (r= −0.408, p = 0.001), but not between the “6-clicks” and age (r= −0.180, p = 0.528). To determine the inter-rater reliability, an additional 50 patients were assessed by pairs of physiotherapists who independently scored the patients. Intraclass Correlation Coefficients of 0.920 (95%CI: 0.828–0.964) were found. The Kappa Coefficients for the individual items ranged from 0.649 (walking stairs) to 0.841 (sit-to-stand). The Dutch “6-clicks” shows a good construct validity and moderate-to-excellent inter-rater reliability when used to assess the mobility of hospitalized patients.Implications for RehabilitationEven though various measurement tools have been developed, it appears the majority of physiotherapists working in a hospital currently do not use these tools as a standard part of their care.The Activity Measure for Post-Acute Care “6-clicks” Basic Mobility is the only tool which is designed to be short, easy to use within usual care and has been validated in the entire hospital population.This study shows that the Dutch version of the Activity Measure for Post-Acute Care “6-clicks” Basic Mobility form is a valid, easy to use, quick tool to assess the basic mobility of Dutch hospitalized patients.