Presents a case report of a 35-year-old patient was admitted to the psychiatric ward for the treatment of gambling addiction. During assessment, the patient reported a history of depressive episodes treated with the following antidepressants: sertraline 100 mg/day, venlafaxine 150 mg/day and citalopram 20 mg/day. However, the treatment was ineffective and full remission of mood disorder was not achieved. During these depressive episodes, increased anxiety and elevated mood were present and the patient engaged in active gambling. On the day of admission, the patient reported the feeling of a strong gambling urge that he found difficult to resist. This case report reveals the necessity for the verification of a mood disorder diagnosis. A medical history that includes a thorough investigation of a patient's past behaviors is extremely important in order to make the right diagnosis and for proper drug treatment. The use of lamotrigine and aripiprazole in combination for the treatment of mixed episode of bipolar disorder was effective in this case.