Anomalies of the fetal urachus are rare. Normally, the postnatal urachus presents as a fibrous band extending from the bladder to the umbilicus. Urachal cysts may occur in postnatal life. Spontaneous perforation of urachal cysts is a very rare condition, which clinically may not be distinguishable from other acute abdominal conditions. We report a case of a 63-year-old male with a history of recurrent urinary tract infections and a bladder rupture caused by a spontaneous perforation of an infected urachal cyst. The symptomatology showed abdominal rigidity and pain, a palpable mass in the lower abdomen, and hematuria. Laboratory findings showed leukocytosis and an increased CRP level. The bladder rupture was confirmed by cystography. Bacteriologic examination identified Proteus vulgaris, Corynebacterium species, and Klebsiella pneumoniae. Most of the published cases in the literature report about intraperitoneal perforation of infected urachal cysts. In the present case, we found a spontaneous perforation of an infected urachal cyst leading to an extraperitoneal bladder rupture with an extraperitoneal limitation of the infection. The definitive therapy was complete surgical excision including a cuff of the bladder, drainage, and systemic broad-spectrum and local application of antibiotics. The further course was uneventful.