Spontaneous regression of cystic adventitial disease of the popliteal artery is rare. In this report, we describe a 54-year-old woman who presented with left calf pain and was diagnosed with cystic adventitial disease with popliteal artery stenosis, which regressed without therapy. The disease was diagnosed via computed tomography, and a surgical intervention was planned at the time of diagnosis. However, her symptoms disappeared 2 months after the initial presentation. Ultrasonography and computed tomography revealed spontaneous regression of the cystic lesions and resolution of the popliteal artery stenosis. During the 29-month follow-up period, her symptoms did not recur. Although CAD often requires surgical intervention, it may be acceptable to carefully observe patients with spontaneous regression for some time to check for recurrence.