Bladder eversion is a rare condition and may occur in mares as a result of excessive straining during pregnancy or in the postpartum period. In the present case, bladder eversion was caused by chronic cystitis in a nonpregnant mare. An Arabian racehorse (mare, 3 years old) was admitted to The Racehorse Hospital of the Turkish Jockey Club with a history of lumbar pain, excessive straining, and frequently assuming the urination position. Physical examination revealed the presence of tenesmus, stranguria, passing of small amounts of urine, and a visible mucosal structure at the ventral vulvar commissure during tenesmus. Laboratory findings revealed leucocytosis, increased urine pH, proteinuria, pyuria, and hematuria. Streptococcus equi subsp. zooepidemicus and Escherichia coli were isolated and identified in urine culture. Transrectal ultrasonography revealed thickening of the bladder wall and prolapse of the bladder corpus into the bladder. In the cystoscopic examination, performed following bladder reduction, severe hyperemia, erosion, and ulcers were determined in the bladder mucosa. Chronic cystitis was treated using antibiotics, based on urine culture test results, together with steroids and non-steroidal anti-inflammatory drugs. Twenty-four hours after the start of treatment, the severity of straining was observed to have decreased, ceasing completely on Day 4, and the bladder returned to its normal position.In this case presentation, bladder eversion caused by chronic bacterial cystitis, diagnosed by clinical, laboratory, ultrasonography, and cystoscopy findings, was evaluated. It was observed that severe inflammation, pain, and straining caused by chronic bacterial cystitis resulted in bladder eversion and that the eversion was corrected with effective medical treatment of the chronic bacterial cystitis. © 2014.