A 3-year old, female Cocker Spaniel dog was referred to Seoul National University Hospital for Animals with depression and vomiting. The dog was diagnosed as hypoadrenocorticism based on the typical electrolyte alteration and the result of adrenocorticotropic hormone (ACTH) stimulation test. Initial treatment with oral fludrocortisone at a dose rate of 0.02 mg/kg/q24h for 6 weeks period was ineffective at maintaining serum electrolyte concentrations within normal limits. Although a dose rate of oral fludrocortisone was significantly increased up to 0.06 mg/kg/q24h during 24 weeks period, the treatment was still ineffective. Moreover, the patient showed side effects related to the glucocorticoid excess including PU/PD, weight gain and lipemia. After alternation with desoxycorticosterone pivalate (DOCP, 2.2 mg/kg, IM) every 25 day, the clinical signs was disappeared and the electrolyte balance was maintain with no side effect. Therefore, DOCP may be suggested as an effective drug in canine hypoadrenocorticism uncontrolled with oral fludrocortisone.