Background Isolated superior mesenteric artery dissection (ISMAD) was previously considered a rare disorder; however, this condition has been increasingly diagnosed as time progressed. Although treatment regimen and treatment outcomes have become clearer, the optimal treatment strategy has not yet been well established. Materials and Methods This study included 54 patients diagnosed with ISMAD by computed tomography (CT) between November 2004 and December 2017. Thirteen patients were excluded from the analysis of natural course as 6 were lost to follow-up, and 7 underwent endovascular therapy. Results Of the 54 patients included in the study, 50 were male, and 4 were female. The mean age of the patients was 52.3 years (range 40–74). The mean follow-up duration was 18.5 months (range 1.0–131.0). Thirty-eight patients were symptomatic, and 16 were asymptomatic. All aneurysmal changes observed on follow-up CT scans were initially classified as type III or IV. Of these patients, 7 underwent endovascular therapy. The failure rate of conservative treatment was 13%. Conclusions Conservative treatment is safe and effective if bowel necrosis or arterial rupture is not present. Symptomatic patients classified as type III or IV on the initial CT scan should be followed up. If there is recurrent pain or aneurysmal progression, endovascular therapy should be performed.