Purpose: The purpose of this study was to explore factors that influence post operative depression in elderly patient. Method: This study was utilized descriptive correlational design. The convenience sample was composed of 82 operational elderly patients in Korea. Stepwise multiple regression was used to identify significant factors influencing postoperative depression in elderly patient. Postoperative depression was measured using the short form Geriatric Depression Scale(GDS), anxiety was measured by the State-Trait Anxiety Inventory, Pain was measured by the Short-Form McGill Pain Questionnaire, family support was measured by Family APGAR. Result: Postoperative depression in elderly patient was significantly influenced by preoperative depression, anxiety, family support. This regression model explained 66%(Adj R2 =.66) of the variances in postoperative depression. Preoperative depression explained 46% of the variances, and anxiety explained 19% of the variances, and family support explained 3% of the variances. Conclusion: Results of this study suggest that nurses intervene more effectively in caring their patients with postoperative patient by recognizing the patients preoperative depression, anxiety, and family support. We suggest that It must be preceded assessment and intervention of preoperative depression in order to intervene postoperative depression.