Background: The distance and angle between the superior mesenteric artery (SMA) and abdominal aorta play a role in the etiology of SMA syndrome. Retroperitoneal fat has been reported to affect both the distance and angle. Very few studies have reported the normal range of these measurements. The present study aimed to evaluate the reference values of the aortomesenteric angle (AMA) and aortomesenteric distance (AMD) in asymptomatic patients, as well as to determine the influence of age, sex, and anthropometric variables on these values. Methods: A retrospective cross-sectional study was conducted at Sultan Qaboos University Hospital. Computed tomography angiography scans of the abdomen from 141 Omani adult patients (aged ≥18 years) were included in the study. The morphometric data of the AMA and AMD were measured at the third part of the duodenum using sagittal and axial multiplanar reconstruction of CTA images. Patient data, including age, sex, height, weight, and BMI, were collected from the medical records. Statistical analyses included the Mann–Whitney U, Kruskal–Wallis H and Jonckheere–Terpstra J-T tests with significance set at p < 0.05. Results: The mean AMA was 57.16 ± 22.06°, and the mean AMD was 21.35 ± 10.25 mm. The AMD varied significantly across age groups (H = 17.29, p < 0.001) and showed a positive trend with increasing age (p = 0.001). Both AMA (p = 0.001) and AMD (p < 0.001) differed significantly across BMI categories, with significant increasing trends (p = 0.033 and p ≤ 0.001, respectively). No statistically significant differences were observed between sexes and study parameters (p > 0.05). Conclusions: The present study demonstrates that the reference values of the AMA and AMD are within the range of those reported in other populations. The variations in these values with BMI and age underscore the importance of individualized imaging interpretation and preoperative planning. The reported baseline data may enhance diagnostic accuracy and assist with surgical planning and radiological evaluation of suspected SMA syndrome.