Primary adrenal lymphoma is a very rare disease and it is known to have a poor prognosis. We report here on a case of primary adrenal insufficiency that was secondary to primary bilateral adrenal lymphoma. A 54-year old man was hospitalized because of easy fatigability, weight loss and consistent malaise for 6 months. The physical examination revealed hyperpigmentation on the anterior chest and hypotension. According these findings and symptoms, we did a rapid ACTH stimulation test with a clinical suspicion of adrenal insufficiency. He showed an inadequate adrenal response and so he was diagnosed with adrenal insufficiency. The abdominal CT images showed bilateral huge adrenal masses and increased uptake of the adrenal glands on PET. The pathologic diagnosis by ultrasound-guided gun biopsy of the right adrenal gland was diffuse large B cell lymphoma. The patient was administered combination chemotherapy with the R-CHOP regimen, and after 8-cycles of chemotherapy, he achieved complete remission of tumor according to the image studies and he recovered his adrenal function. Primary adrenal lymphoma, although a rare disease, should be considered in patients with bilateral enlargement of the adrenal glands and when the adrenal glands show increased uptake on a PET scan, and especially there is adrenal insufficiency.