The administration of cyclophosphamide (CP) is associated with the risk of developing cystitis as well as kidney injury. The aim of the study was to verify the uroprotective effect of N-acetylcysteine (NAC), as well as the evaluation of renal function in the experimental model of acute CP-induced cystitis. Rats from group 1 received intraperitoneally only a single dose of 200 mg/kg b.w. of CP. Individuals from groups 2 and 3 additionally received a single dose of 200 mg/kg b.w. of NAC, respectively, orally (p.o.) and intraperitoneally (i.p.). After the administration of the drugs, animals were subject to individual monitoring in metabolic cages to assess 24-hour diuresis and basic vital signs, and then finally sacrificed for the purpose of collecting blood and organs for histopathological analysis. Classic renal parameters (creatinine, urea, uric acid, electrolytes) as well as new markers reflecting renal function, within the filtration-resorption range - cystatin C (CysC), renal tubular integrity - kidney injury molecule-1 (KIM-1) and the condition of the glomerular filtration barrier (nephrin) were determined in the obtained serum and urine samples. In group 1 histopathological development of cystitis was confirmed with the absence of significant pathomorphological disorders of the kidneys, and the initial results of the parameters determined were obtained. In both groups 2 and 3, a decrease of inflammatory changes in urinary bladder was observed, while there were still no morphological disturbances in kidneys. The administration of NAC in both groups 2 and 3 also resulted in a decrease of concentrations in urine and a reduction in 24-hour excretion with urine of all assessed proteins (CysC, KIM-1 and nephrin). NAC, thus exhibited a uroprotective effect, which was accompanied by a functional nephroprotective effect (more accentuated during intraperitoneal administration of this compound), manifested by the reduction of urinary excretion of proteins indicative of developing renal dysfunction.