Background <p>To our knowledge, the current status of and barriers to cancer rehabilitation in palliative care units (PCUs) in Japan remain to be elucidated. If clarified, this information could help develop rehabilitation strategies to improve the quality of life of patients with cancer who need palliative care. Hence, this study aimed to clarify the current status of and barriers to cancer rehabilitation in PCUs in Japan by conducting a nationwide questionnaire survey.</p> Methods <p>This nationwide questionnaire-based survey included 462 hospitals that met the facility criteria for PCU inpatient charges, and notified local health authorities. The questionnaire included questions on the implementation rate of cancer rehabilitation, the sufficiency/insufficiency of cancer rehabilitation and its reasons, and the reasons for and need not implement cancer rehabilitation in PCUs.</p> Results <p>Among the 462 hospitals, we received responses from 268 hospitals (response rate: 58.0%). Cancer rehabilitation was implemented in 244 (91.0%) responding hospital PCUs. Among the implementing hospitals, 155 (63.5%) recognized cancer rehabilitation as inadequate. The main reasons for this insufficiency were ineligibility for medical fees for disease rehabilitation and a lack of rehabilitation staff. Among the non-implementing hospitals, the main reasons for not implementing cancer rehabilitation were ineligibility for medical fees for disease rehabilitation and a lack of rehabilitation staff. Of the non-implementation hospitals, 76.2% (<i>n</i> = 16) indicated the need for cancer rehabilitation in their PCUs.</p> Conclusions <p>To ensure sufficient and quality-assured cancer rehabilitation in PCUs, it is necessary to allocate medical fees for disease rehabilitation, provide additional reimbursements, and increase the number of rehabilitation staff.</p>