Feline lower urinary tract diseases are known to be life threatening conditions in cats, especially when they occur as obstructive diseases in males. Early diagnosis and treatment is necessary, otherwise it may lead to death. A 3-year-old male Persian cat was referred to the clinic with a history of anuria, lethargy, loss of appetite and exploratory cystotomy 6 months ago due to urethral obstruction following urolithiasis. Urinary bladder was enlarged and painful on palpation and urine accumulation was observed in ultrasonography. Biochemical and hematological analyses revealed hypocalcemia, hyperphosphatemia and hyperkalemia and increase in blood urea nitrogen, creatinine, white blood cell (WBC), red blood cell (RBC) and hematocrit. Urine analysis showed a turbid appearance, protein 1+, blood 3+, pH reduction, increased WBCs and RBCs and presence of bacteria, calcium oxalate crystals and epithelial cells. Urine culture reveled Staphylococcus saprophyticus. Postoperatively, microscopic examinations of the urinary bladder biopsy showed pathological lesions of bacterial cystitis. Based on these findings, bacterial cystitis and urethral obstruction due to post-operative urinary tract infections were diagnosed. For treatment, electrolyte imbalances were corrected firstly, cystotomy was performed and a catheter was conducted into the urethra; then, urethra was flushed and obstruction was resolved. Ampicillin was effective in reducing the bacterial count in urine. Despite the fact that cystotomy is a common procedure in veterinary medicine, clinicians should be aware of its complications such as post-operative urinary tract infections.