Peritoneal carcinomatosis in prostate cancer is extremely rare and has been described in only few cases with high PSA level, androgen deprivation, or in symptomatic patients. To date, 2 cases of Ga-PSMA PET positive peritoneal metastases have been reported. We report a case of urachus metastases showed on Ga-PSMA PET/CT performed for biochemical recurrence with a very low PSA level at 0.50 ng/mL.