Objective Internationally, the Distress Thermometer and associated Problem List are increasingly used in oncology as screening tools for psychological distress. Cancer‐related fatigue is common but often overlooked in clinical practice. We examined if severe fatigue in cancer patients can be identified with the fatigue item of the Problem List. Methods Newly diagnosed breast (N = 334) and colorectal (N = 179) cancer patients were screened for severe fatigue, which was defined as having a positive score on the fatigue item of the Problem List. The Fatigue Severity subscale of the Checklist Individual Strength was used as gold standard measure for severe fatigue. Results In total, 78% of breast cancer patients and 81% of colorectal cancer patients were correctly identified with the fatigue item. The sensitivity was 89% in breast cancer patients and 91% in colorectal cancer patients. The specificity was 75% in breast cancer patients and 77% in colorectal cancer patients. The positive predictive value was 53% in breast cancer patients and 64% in colorectal cancer patients, whereas the negative predictive value was 95% in both tumor types. Conclusions The fatigue item of the Problem List performs satisfactorily as a quick screening tool for severe fatigue. However, a positive screen should be followed up with a more thorough assessment of fatigue, ie, a questionnaire with a validated cutoff point. Given time pressure of clinicians, this already implemented and brief screening tool may prevent severe fatigue from going undetected in clinical practice.