Objective: The Japanese version of Edmonton Functional Assessment Tool 2 (EFAT2-J) is a physical function assessment specifically for patients with advanced cancer. The purpose of this study was to examine the responsiveness of the EFAT2-J total score and to determine the clinical usefulness of the EFAT2-J. Methods: Participants were cancer patients who were being treated by a palliative care team and were not receiving curative treatment. Responsiveness was determined by comparing and correlating changes in the EFAT2-J and existing assessment scales up to approximately 2 weeks after the start of rehabilitation and calculating the standardized response means (SRM). Results: The participants were 31 patients with advanced cancer. The SRM of the EFAT2-J was large, and those of the existing assessment scales were moderate and small. Discussion: The EFAT2-J is an excellent physical function assessment that accurately captures changes in physical function in patients with advanced cancer.