Aneurysms of the superior mesenteric artery (SMA) and its branches are rare and account for only 6% to 15% of all visceral artery aneurysms. In the present report, we have described our 30-year experience with the management of aneurysms of the SMA and its branches at a high-volume referral center. A retrospective review of all patients with a diagnosis of an aneurysm of the SMA or one of its branches from 1988 to 2018 was performed. Pseudoaneurysms and mycotic aneurysms were excluded. The clinical presentation, etiology, aneurysm shape and size, treatment modalities, and outcomes were analyzed. The growth rate of the aneurysms was estimated using linear regression. A total of 131 patients with 144 aneurysms were reviewed. The patients were primarily men (64%), with a median age of 60 years. Of the 144 aneurysms, 57 were fusiform, 30 were saccular, and 57 were dissection-associated aneurysms. Of the 131 patients, 41 had had an isolated SMA branch aneurysm. Degenerative aneurysms were the most common etiology (66%). A total of 35 patients (27%) were symptomatic at presentation. Of the 144 aneurysms, 111 had multiple computed tomography angiograms available, with a median follow-up of 43.6 months (interquartile range, 10.6-87.2 months). Only 18 aneurysms (16%) had had an estimated growth rate of ≥1.0 mm/y. The initial aneurysm size was significantly associated with the growth rate for the fusiform aneurysms (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.0-1.3]; P = .02) but not for the saccular (OR, 0.91; 95% CI, 0.76-1.1; P = 1.1) or dissection-associated (OR, 1.2; 95% CI, 0.91-1.5; P = .20) aneurysms. Acute abdominal pain (OR, 5.9; 95% CI, 1.6-22; P = .01) and chronic abdominal pain (OR, 3.7; 95% CI, 1.1-13; P = .04) were associated with aneurysm growth. Only two patients had a ruptured aneurysm, both of whom presented with rupture with no prior imaging studies. These two patients had a diagnosis of fibromuscular dysplasia and systemic lupus erythematosus, respectively. Of the 131 patients, 46 (34%) had undergone operative repair, including 36 open revascularizations and 8 endovascular procedures. The average aneurysm size for these 46 patients was 24.0 ± 8.6 mm. One patient died perioperatively, and nine patients experienced perioperative complications (25%). Of the 144 aneurysms, 91 were <20 mm, with an average size of 13.4 ± 3.1 mm. These 91 aneurysms had been followed up for a median of 120.8 months (interquartile range, 30.5-232.2 months), with no ruptures within this cohort during the follow-up period. The present study represents one of the largest series on aneurysms of the SMA and its branches. Our results showed that aneurysms of the SMA are relatively stable. Patients with symptomatic and fusiform aneurysms had a greater risk of growth. Aneurysms <20 mm with a degenerative etiology can be safely monitored without treatment.