Introduction: Stress urinary incontinence affects up to 50% of women at some point in their lives. Tension-free vaginal mid-urethral sling procedure should be offered as a primary surgical treatment option to women with stress urinary incontinence. Case Report: We report on the case of a 47-year-old patient presenting with heavy buttock and thigh pain, a severe walking disability necessitating the use of a walker after implantation of a retropubic sub-urethral sling (TVT-SERASIS) for the treatment of stress urinary incontinence in an external hospital. During the surgery in our hospital, it was revealed that the sling was placed incorrectly, charging the bladder wall as well as the left obturator nerve. We describe the diagnosis and operative management of this rare, but serious complication. Conclusion: Our case provides supporting evidence for the limited value of imaging tools and the need of a surgical exploration under certain circumstances. In addition, we emphasize that removal of a sub-urethral sling should be performed under laparoscopic visualization when serious adverse events occur. Sub-urethral sling placement should be executed by experienced, dedicated pelvic floor surgeons.