Assessing suicide risk remains a challenge for clinicians. Thoughts about suicide and/or death usually precede suicide attempts, patients do not always reveal these thoughts to clinicians. Much research has found a tendency for patients to admit suicidal ideation in self-report instruments and then deny it in clinician assessment. In this light, we assessed the level of agreement about suicidal ideation assessed by clinicians and self-reported by patients and in a sample of adult patients during routine psychiatric or psychological appointments in outpatient mental-health facilities. Furthermore, we used cluster analysis to determine the clinical profile of patients according to the concordance between patients and clinicians. The study took place between 2014 and 2016 in Fundación Jiménez Díaz Hospital in Madrid, Spain. During the routine appointment, clinicians assessed suicidal ideation with the question “Have you ever thought that you would be better off dead or wish you were dead?”. Patients were provided with access to web-based self-report questionnaire in which the same construct was assessed with the question “Have you ever felt that you had no desire to live?” In the 24 hours after clinician assessment, 648 patients completed the questionnaire. A low level of agreement (kappa=0.072) was found between clinicians and patients, as 56.4% (n=366) of clinician reports classified as containing no death-related ideas although on self-report the patient did state that they had no desire to live. In this group containing discrepancies between the two reports, two clusters were found to have shared characteristics: female sex, middle age, cohabitation, active employment, no history of suicidal behavior, and diagnosis of neurotic, stress-related, and somatoform disorders. In a third, more severe cluster, patients self-reported sleep disturbances, less appetite, poor treatment adherence, and aggressiveness. Our results suggest that clinicians require adequate documentation of suicidal risk assessment to identify high-risk populations; otherwise, the risk of underestimation is high, and the consequences could be fatal. Our findings point to a need to introduce user-friendly instruments that may aid clinical assessment by enhancing reliability and validity in diagnosis and suicide risk assessment.