Purpose Cases of cancer-related fatigue syndrome (CRFS) can be reliably indentified using a diagnostic interview combined with a structured psychiatric interview. However, these interviews are time consuming to conduct, require specialist training, and are not suitable for routine clinical use. The purpose of this study was to identify whether a screening questionnaire could identify patients at high risk of clinically significant fatigue who should be considered for a suitable intervention. Patients and Methods The diagnostic interview for CRFS and the structured clinical interview for the diagnostic and statistical manual of mental disorders were used in order to identify breast cancer survivors who fulfilled the criteria for CRFS. Two fatigue questionnaires (the Bidimensional Fatigue Scale [BFS] and the Functional Assessment of Cancer Therapy-Fatigue subscale [FACT-F]) were administered in order to determine their screening properties. Results Two hundred women were interviewed and 60 women fulfilled the criteria for CRFS. The BFS cutoff score of 11 had a sensitivity of 92%, a specificity of 53%, a positive predictive value (PPV) of 46%, and a negative predictive value (NPV) of 94%. The FACT-F cutoff score of 36 had a sensitivity of 80%, a specificity of 71%, a PPV of 55%, and a NPV of 89%. Conclusion The BFS and FACT-F cutoff scores can be used to identify breast cancer survivors at higher risk of clinically significant ongoing post treatment fatigue. Neither scale can be used as a diagnostic instrument for CRFS.