The proportion of elderly patients who undergo surgery has rapidly increased; however, clinical indicators predicting outcomes are limited. Our aim was to evaluate the significance of comprehensive geriatric assessment (CGA) in elderly patients undergoing elective surgery. We studied 141 consecutive elderly patients (age: 78.0±6.5 years old, male: 41.1%) who were referred to our geriatric department for surgical risk evaluation. CGA was performed to evaluate physical health, functional status, psychological health, and social support. The primary composite outcome of this study was in-hospital death or post-discharge institutionalization. In-hospital adverse events, such as delirium, pressure ulcers, pneumonia, and urinary tract infections, were also evaluated. The associations between CGA and in-hospital adverse events, in-hospital death, and post-discharge institutionalization were investigated. There were 32 adverse outcomes (6 in-hospital deaths and 26 post-discharge institutionalizations). Compared with the patients who were discharged to their homes, patients with adverse outcomes were characterized by poor nutritional status and prior strokes. However, there was no significant difference in surgical risk or anesthesia type. The CGA results showed that patients with adverse outcomes were associated with functional dependency and poor nutrition. The cumulative number of impairments in the CGA domain was significantly associated with adverse outcomes, in-hospital events, and prolonged hospital stays. In multiple logistic regression analysis, cumulative impairment in CGA was independently associated with surgical outcomes in elderly patients undergoing elective surgery. Preoperative CGA can identify elderly patients at greater risk for mortality, post-discharge institutionalization, adverse in-hospital events, and prolonged length of hospital stay.