We report an unusual case of a bladder stone which formed on a non-absorbable suture in a woman with a previous cesarean section. After endoscopic disintegration of the stone, a ring-shaped silk suture which was encrusted in the bladder stone was unveiled. Based on the literature, most foreign bodies in the bladder are subject to stone formation on the bladder wall, but rarely become encrusted into a stone within the bladder. However, our patient's bladder wall was intact, and the bladder stone had a normal appearance without evidence of enclosure by a foreign body. In our opinion, we suggest that bladder stone formation should be excluded in the clinical evaluation of women with recurrent urinary tract infections (UTIs). Therefore, complete evaluation including urinalysis, and imaging studies such as x-ray, ultrasound, and cystoscopy are necessary to assess recurrent UTIs.