ABSTRACTIt is crucial to develop practical and noninvasive methods to assess the functional beta‐cell mass in a donor pancreas, in which monitoring and precise evaluation is challenging. A patient with type 1 diabetes underwent noninvasive imaging following simultaneous kidney–pancreas transplantation with positron emission tomography/computed tomography (PET/CT) using an exendin‐based probe, [¹⁸F]FB(ePEG12)12‐exendin‐4. Following transplantation, PET imaging with [¹⁸F]FB(ePEG12)12‐exendin‐4 revealed simultaneous and distinct accumulations in the donor and native pancreases. The pancreases were outlined at a reasonable distance from the surrounding organs using [¹⁸F]FB(ePEG12)12‐exendin‐4 whole‐body maximum intensity projection and axial PET images. At 1 and 2 h after [¹⁸F]FB(ePEG12)12‐exendin‐4 administration, the mean standardized uptake values were 2.96 and 3.08, respectively, in the donor pancreas and 1.97 and 2.25, respectively, in the native pancreas. [¹⁸F]FB(ePEG12)12‐exendin‐4 positron emission tomography imaging allowed repeatable and quantitative assessment of beta‐cell mass following simultaneous kidney–pancreas transplantation.