Objective To evaluate the value of ¹⁸F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (¹⁸F-FDG PET/MRI) in the diagnosis of postoperative recurrence of pancreatic cancer. Methods The study included 86 consecutive patients after resection of pancreatic cancer from April 2018 to December 2023, who underwent ¹⁸F-FDG PET/MRI from August to September 2024. The efficacy of 1¹⁸F-FDG PET/MRI in detecting postoperative recurrence of pancreatic cancer was retrospectively analyzed, and compared with that of serum carbohydrate antigen 19-9 (CA19-9) concentration in the diagnosis of recurrence. Results Follow-up confirmed that 67.4% (58/86) of patients experienced recurrence. The primary tumor diameter in the recurrence group (3.4±1.3cm) was larger than in the non-recurrence group (2.7±1.2cm). Among the patients with recurrence, 87.9% (51/58) had systemic recurrence, with the most common sites being liver metastasis and peritoneal metastasis. PET/MRI results changed the treatment plans for 30.2% (26/86) of patients. Among the 86 cases, 79 patients underwent both PET/MRI and serum CA19-9 tests. PET/MRI showed higher diagnostic efficacy for detecting postoperative recurrence of pancreatic cancer compared to serum CA19-9 (AUC: 0.847 vs. 0.719 ). PET/MRI detected 9/12 cases of pancreatic cancer recurrence with normal serum CA19-9 levels, and excluded 5/8 patients with elevated serum CA19-9 levels who did not experience recurrence. Conclusions PET/MRI has great clinical value in the diagnosis of postoperative recurrence of pancreatic cancer. It is particularly meaningful for patients with normal serum CA19-9 level. It can not only diagnose recurrence but also provide the specific site of tumor recurrence and comprehensive information for the formulation of the next treatment plan.