Diseases of the bladder and urethra are more common and more important than diseases of the kidneys in large animals. However, limited studies have been done in the case of bladder diseases in small ruminants. The purpose of this investigation was to determine the frequency of urinary bladder lesions in small ruminants at Garmsar abattoir. Based on a cross-sectional study 400 randomly selected small ruminant's bladders (315 sheep and 85 goats) were examined at the local slaughterhouse in summer and autumn. Species, age and sex of the animals and characteristics of the observed lesions were recorded. Types of the lesions were determined by histopathological examination. Chi-square and Fisher's exact tests were used for data analysis. Of the 400 urinary bladders, the rate of frequency was calculated 18(4.5%) and the range was estimated as 2.69-7.02% using 95% level of confidence. The prevalence of urinary bladder lesions were 2.86% in sheep and 10.59% in goats. The lesions included parasitic cyst, melanosis, developmental abnormality of mucosa, diverticulum, transitional cell papilloma and leiomyoma.