A 72-year-old male with a history of prostate cancer and high prostate specific antigen levels underwent 99mtechnetium-methylene diphosphonate (99mTc-MDP) single-photon emission computed tomography/computed tomography (SPECT/CT), to identify bone metastasis. The patient possessed no previous history of serious illnesses or surgical procedures and no family history of malignancies. A whole-body CT scan revealed an intense MDP uptake in the right inguinal region on the anterior view, but not in the posterior view, which was suspected to be a metastatic lesion. However, there was no evidence of bone metastasis on the CT scan. In addition, an increased 99mTc-MDP uptake was indicated on the SPECT images in the right inguinal region, which appeared to be separate from the main bladder activity. CT images of the pelvis revealed an inferior tongue-like extension of the bladder into the right inguinal region. Fused SPECT/CT axial images indicated the circular accumulation of the 99mTc-MDP in the medial right groin, with well-defined walls that connected the accumulation to the bladder. The final diagnosis was a bladder hernia (T2N0M0), which may have been responsible for the misdiagnosis of bone metastasis due to the use of radiopharmaceuticals (99mTc-MDP) that were mainly excreted through urination. Considering the comprehensive situation of the patient, radical prostatectomy was performed. The bladder hernia was subsequently monitored by follow-up examination every 3 months, and remains alive and under follow-up to date.