Apparent diffusion coefficient (ADC) values at magnetic resonance imaging (MRI) are useful to distinguish vasogenic and cytotoxic edema due to cerebovascular diseases. Dural arteriovenous fistulas (DAVFs) with retrograde leptomeningeal venous drainage may cause cerebral edema by venous congestion. We report herein the course of ADC values of cerebral edema before and after endovascular treatment in DAVFs. A 65-year-old woman with transverse-sigmoid (T-S) sinus DAVFs with retrograde leptomeningeal venous drainage presented with severe edema in cerebellar hemisphere and brainstem. In preoperative MRI, increased ADC values were observed in the edema area. The isolated sinus was obliterated completely by transvenous embolization. On the following day after treatment, the ADC values in cerebral edema area increased slightly without any new neurological deficits and improved at 1 week later. Rapid resolution of venous congestion due to DAVFs may cause a slight, transient progression of vasogenic edema.