Cystitis is a common problem in companion animal practice, and common cause of morbidity in dog population. The present work was conducted to evaluate Clinical, haematological and biochemical analysis in dogs suffered from cystitis. The study was carried out in small animal internal medicine teaching hospital, faculty of Veterinary Medicine, Cairo University. About 56 dogs of different ages, sex, and breeds were enrolled in this study. Fourteen (14) of dogs used as control group and 42 cases dogs suffered from cystitis (acute and chronic), All dogs were subjected for through clinical (case history, physical examination, ultrasonography, urinalysis and urine culture), hematological and biochemical investigation. Clinical examination reveal red discoloration of urine  ,dysuria with painful  attempt to micturate, pollakuria, stranguria, periuria ,painful  belly palpation  with distended urinary bladder , significant increase in pulse rate, and non significant increase in temperature and respiratory rate. Hematological analysis revealed significant decrease in Hb, RBCs and MCHC, significant increase in total leukocytic count (TLC) with significant decrease in segmented neutrophils. Biochemical analysis revealed no change in urea, creatinine and uric acid. Macroscopic Urinalysis showed blood, leucocytes, protein, while increased numbers of WBCs, RBCs, bacteria and crystals of uric acid and triple phosphate were detected in microscopical examination. Urine culture revealed isolates of E-coli, Proteus and Staphylococcus. Ultrasonography of urinary bladder of dogs suffered from cystitis show thickening in the wall of the bladder with hyper echoic layers. So we conclude that alteration in clinical (physical examination, Ultrasonography and urinalysis) and  hematological result may be indicative for the diagnosis of cystitis in dogs, but biochemical result reveal non significant change.