Delirium is an acute state of impaired consciousness and a medical urgency. Its broad range of alterations in mental status make diagnosis challenging. Awareness and accurate provisional diagnosis by nonpsychiatric clinicians are important for prompt management. Because delirium symptoms overlap and mimic other neuropsychiatric conditions, a referral to a consultant psychiatrist is often needed. The aim of this study was to determine the discriminating variables that are associated with concordance or discordance for a DSM-5 delirium diagnosis made by the consultation/liaison (C/L) psychiatrist as compared to the referral diagnosis/reasons given by the referring physicians for inpatients from a Tertiary Hospital in a Latin-American country. Prospective study of a cohort of 399 consecutive patients admitted to any ward of a university hospital in Medellin-Colombia and referred by a specialist physician to the C/L Psychiatry service. Analyses for diagnostic concordance used a nested sample of 140 cases diagnosed with delirium by the psychiatrist. Two multivariate logistic models were run, for delirium diagnosis concordance and discordance between the referring physician and C/L psychiatrist. The referral diagnosis was concordant with that of Psychiatry in 90/140 patients in 64.3%, with 35.7% discordance. Increasing age (OR = 1.024) and internal medicine ward (OR = 3.0) were significantly related (Wald statistic P < .05) to concordance in the multivariate analysis whose model accuracy was 68.6%. Trauma/orthopedics ward (OR = 5.7) and SARS-CoV-2 infection (OR = 3.8) were important contributors to the model fit though not significant. Accuracy of the discordance model was 70.7%, where central nervous system (CNS) disorder (OR = 6.1) and referrals from ICU (OR = 4.9), surgery (OR = 4.6), neurology/neurosurgery (OR = 5.1) and another consultant (OR = 4.7) were significantly related (Wald statistic P < .05), while metabolic/endocrine disorder (OR = 2.7) was important for model fit, but not significant. Concordance for delirium diagnosis was higher from services where education, guidelines and working relationships with C/L Psychiatry could have contributed beneficially whereas, surprisingly, CNS disorders and neurology/neurosurgery services had higher discordance, as well as the ICU. Routine use of brief sensitive delirium assessment tools such as the DDT-Pro could enhance provisional delirium diagnosis.