Objective To evaluate the value of enhanced magnetic resonance imaging (MRI) in the preoperative diagnosis of Siewert type Ⅱ/Ⅲ adenocarcinoma of esophagogastric junction (AEG). Methods The imaging data of 76 patients with Siewert type Ⅱ/Ⅲ AEG confirmed by postoperative pathology from Jan. 2018 to May 2020 in our hospital were retrospectively analyzed. Two attending physicians measured and diagnosed the lesions on enhanced computed tomography (CT) and enhanced MRI images by blind method. The consistency between the 2 examination results and pathological results was analyzed by Kappa test. Results All 76 patients underwent imaging examination within 1 week before surgery:27 cases underwent enhanced CT only, 9 cases underwent enhanced MRI only, and 40 cases underwent both (with an interval of 1 d). A total of 67 preoperative enhanced CT images and 49 preoperative enhanced MRI images were obtained. Among the 67 patients with AEG who underwent enhanced CT, there were 35 cases of Siewert type Ⅱ and 32 cases of Siewert type Ⅲ, and the diagnosis was correct in 56 patients, showing moderate agreement with the pathological results (Kappa=0.672). Among the 49 patients with AEG who underwent enhanced MRI, there were 27 cases of Siewert type Ⅱ and 22 cases of Siewert type Ⅲ, and the diagnosis was correct in 44 patients, showing good agreement with the pathological results (Kappa=0.791). The positive metastatic lymph nodes suggested by preoperative enhanced MRI were not consistent with the postoperative pathological results (Kappa=0.115), and the positive metastatic lymph nodes suggested by enhanced CT were also not consistent with the postoperative pathological results (Kappa=-0.129). With the pathological results as the gold standard, the accuracy of enhanced MRI in grouping positive metastatic lymph nodes was 59.2% (29/49), which was higher than that of enhanced CT (41.8%[28/67]). Conclusion The accuracy of preoperative enhanced MRI for Siewert classification and grouping areas of positive metastatic lymph nodes in AEG patients is higher than that of enhanced CT, which may provide favorable evidence for the clinical treatment, choice of surgical route and extent of lymph node dissection.