ContextThe Edmonton Symptom Assessment System–revised (ESAS-r) is a brief and widely used symptom measurement tool. ObjectivesTo validate the Japanese version of the ESAS-r in Japanese patients with cancer. MethodsWe assessed the internal consistency, test-retest reliability, concurrent validity, and known-group validity in 292 Japanese adult patients with cancer. They completed Japanese versions of the ESAS-r, M. D. Anderson Symptom Inventory, and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire–Core 30. ResultsCronbach's alpha coefficient of the Japanese version of the ESAS-r was 0.87. The intraclass correlation coefficient in the test-retest examination ranged from 0.82 to 0.91 for each symptom score and was 0.90 for the total score. Pearson correlation coefficients of each ESAS-r symptom score with corresponding M. D. Anderson Symptom Inventory and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire–Core 30 items ranged from 0.45 to 0.80. The total score of the ESAS-r was significantly higher in patients with an Eastern Cooperative Oncology Group performance status of 2–4 than in those with a performance status of 0 and 1 (P < 0.0001). ConclusionThe Japanese version of the ESAS-r is a reliable and valid tool for measuring symptoms in Japanese adult patients with cancer.