Transient receptor potential melastatin 8 (TRPM8) has a role in the abnormal sensory transduction of the bladder and is involved in the pathophysiology of hyperactivity bladder disorders. In the present study, we examined the effects of KPR-5714, a novel and selective TRPM8 antagonist, on voiding dysfunction induced by bladder afferent hyperactivity via mechanosensitive C-fibers in rats. In cystometry measurements, the intercontraction interval was decreased by intravesical instillation of 10 mM ATP in female rats. KPR-5714 dose-dependently prolonged the shortened the intercontraction interval provoked by ATP. In voiding behavior measurements, intratesticular injection of 3% acetic acid and water avoidance stress exposure decreased the mean voided volume and increased voiding frequency in male rats. KPR-5714 dose-dependently increased the mean voided volume and decreased voiding frequency without affecting the total voided volume in these rats. However, KPR-5714 did not influence the voiding behavior in normal rats. These results suggest that KPR-5714 improves voiding dysfunction by inhibiting the enhanced activity of mechanosensitive bladder C-fibers in rats with bladder overactivity and does not affect normal voiding behavior.