Systemic diseases, vascular and/or lymphatic system abnormalities, non-steroidal anti inşammatory and antihypertensive drugs, steroid, immunotherapies, calcium channel blockers and alpha adrenergic antagonists can cause edema. Olanzapine unusually can cause peripheral edema. Some hypothesis about how olanzapine can cause peripheral edema was proposed. In this article, here we present a case of a 41-year-old female patient with bipolar disorder. The patient has a history of dirtiness obsessions and cleaning compulsions for nine years but she has not used any psychiatric medication until her symptoms increased and insomnia, anxiety, anhedonia were added. She had the diagnosis of OCD and MDD and the treatment of şuvoxamine and trazodone was started in the other hospital which she applied. Two weeks later, she applied our hospital with the symptoms of irritability, discomfort, distractibility, decrease in the need for sleep and increases in speak and activity adopted for a purpose, then she was hospitalized in our inpatient clinic. In her examination with SCID-1, she had the diagnosis of bipolar disorder manic episode according to the criteria of DSM-IV-TR and valproate 1000 mg/day and olanzapine 5 mg/day were started. Two weeks later, she was discharged with the same treatment. Bilateral pedal edema was observed in the fourth month of the treatment. In the examination according to other etiological factors, like echo cardiography and bilateral lower extremity venous system doppler, no pathology was found. Serum electrolyte values, renal function tests, thyroid function tests and complete blood count results were normal. No pathological sign was found in the consultation of internal medicine. The patient reported that there is no change in her diet and liquid intake. Olanzapine 5 mg/day was ceased by decreasing gradually. One week later, in her physical examination it was observed that bilateral pedal edema regressed. The clinicians should be aware that bilateral pedal edema can occur in the patients who are treated with olanzapine.