Objectives: Depression may be under-diagnosed and under-treated amongst older adults with multiple chronic illnesses. The current study explores the prevalence of depression diagnosis and Geriatric Depression Scale (GDS) symptoms amongst older multimorbid outpatients, and agreement between GDS scores and doctor-diagnosed depression. Method: Deidentified data from the files of 452 patients aged over 64, with chronic conditions present in two or more organ domains, were extracted from the clinical database of a tertiary referral hospital multidisciplinary outpatient clinic in South Australia between 2005 and 2011. Frequency calculations determined the prevalence of depression diagnosis and GDS categories. Logistic regression, cross-tabulation, kappa and ROC graphs explored relationships between variables. Results: A depression diagnosis had been recorded for 71 (15.7%) patients. Using the recommended cut-off scores for the GDS, 225 (49.8%) patients met criteria for mild-severe depressive symptoms, and 96 (21.3%) met criteria for moderate-severe symptoms. Poor agreement was found between doctor diagnosis of depression and a positive screen for depression using a GDS cut-off score of either 5, k = 0.112 (p = 0.001), or 9, k = 0.189 (p < 0.001), although logistic regression found an association between severity of depression and depression diagnosis, OR = 1.15, p < 0.001 (CI = 1.08 - 1.22). Conclusion: A much higher proportion of patients with multimorbidities reported threshold level depression symptoms than had a recorded diagnosis of depression, suggesting that although likelihood of diagnosis increases with symptom severity, depression often goes undetected in this population. Depressions’ negative impact on prognosis calls for further investigation of the barriers to screening and diagnosis of depression in multimorbid patients.