The modified Richmond Agitation-Sedation Scale (RASS) seems to be one of the best monitoring indicators for palliative sedation. We translated the modified RASS into Japanese according to the standard methods of conducting linguistic validation. The modified RASS revised two points from the original RASS for use in palliative care setting: deleted the description about the ventilator, and added some descriptions to clarify the meaning of RASS+1. In addition, we have deleted the description “rubbing sternum” in the procedure for RASS assessment, and then translated the modified RASS into Japanese. The translators and our research team members repeatedly discussed the linguistic validity until we agreed that the translated Japanese version is equivalent to the English one. The use of the Japanese version of the modified RASS to monitor palliative sedation may help to perform appropriate, and safe palliative sedation.