All-trans retinoic acid (ATRA) is a potent differentiating agent for the treatment of acute promyelocytic leukemia (APL). Although ATRA is generally well-tolerated, some patients develop side effects, the most severe of which is ATRA syndrome. We report on a patient with APL who developed isolated nephrotic-range proteinuria during ATRA therapy for remission-induction. ATRA was discontinued and the proteinuria decreased significantly 5 days after dexamethasone treatment. The occurrence of isolated proteinuria during ATRA treatment is a rare adverse event.