Background/aim: The Cancer Fatigue Scale (CFS) was developed to evaluate the severity of fatigue in patients with breast cancer. The aim of this study is to translate and culturally adapt a Turkish version and investigate the validity and reliability of the CFS in Turkish patients with fatigue symptoms. Materials and methods: Eighty participants completed the Turkish version of the CFS for breast cancer and the European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire ″Core 30″ (EORTC QLQ-C30). Test-retest reliability was evaluated by repeating the CFS with a 7-day interval. Results: The CFS demonstrated high test-retest reliability (ICC = 0.95) and good internal consistency (Cronbach′s alpha = 0.74) for all domains. The Kaiser-Meyer-Olkin measure of sampling adequacy was found to be 0.819, which is considered to be satisfactory (>0.5). Correlations between domains of CFS physical and EORTC physical (r: 0.77), CFS cognitive and EORTC cognitive (r: 0.70), and CFS physical and EORTC fatigue (r: 0.80) were found to be significant. Conclusion: The Turkish version of the CFS is a reliable and valid instrument to assess physical, effective, and cognitive dimensions of fatigue. The CFS may be used to evaluate the severity of fatigue in Turkish-speaking breast cancer patients.