Background: The distress of patients suffering from a terminal illness can lead to a state of despair and requests for euthanasia and assisted suicide. It is a major challenge for palliative care workers. The Distress Thermometer (DT) is recommended by the National Comprehensive Cancer Network as a means of more easily assessing distress. It is available as a Self-assessment reported Distress Thermometer, but for a wider use in palliative care it should also be implemented in the form of a clinician-reported outcome (clinRO). Clinicians need to rate patient's distress when the patient is not able to do so (subject that cannot be addressed, defensive patient…). The primary aim of the quantitative study was to assess the validity of the Clinician-Rated Distress Thermometer in palliative care. Method: The assessments were performed by teams working in three palliative care centres. The primary endpoint was concordance between the patient and clinicians' responses via Lin's concordance coefficient. Eligible patients were aged 18 years or older, suffering from a severe disease in the palliative phase, and with a sufficient level of awareness to consent to participate in the study. A total of 51 patients were recruited, 55% were male, with a mean age of 65.8 years [39-90 years]. Results: Three hundred sixty-four clinician-Rated Distress Thermometer and 467 Self-Reported Distress Thermometer were performed. Only 364 of the 467 Self-Reported Distress Thermometer were used for the study, as investigators did not systematically ask the patient to give an account of his distress. Concordance between patient and clinician responses: The Lin's concordance coefficient with a threshold (alpha) of 5% was 0.46 [0.38; 0.54]. At the first assessment, it was 0.61 [0.44; 0.79]. The Cohen's kappa coefficient was 0.52, with a concordance rate of 79.6%. The sensitivity was 82.9% [66.4-93.4] and the specificity 71.4% [41.9-91.6]. Conclusion: The first assessment gave the best results in terms of concordance between Clinician-Rated DT and Self-Reported DT. In the next assessments, the Clinician-Rated DT were less consistent with the patients' Self-Reported DT.