Due to severe dysmenorrhoea a 29-year-old woman, gravida 2 para 2, was diagnosed with a unicornuate uterus and a rare variety of a rudimentary uterine horn associated with two separate non-communicating cavities. Increasingly intense dysmenorrhoea, refractory to medical treatment, motivated fertility-sparing surgical treatment. A da Vinci S-HD robot was side-docked to facilitate simultaneous vaginal access during surgery. After sacrificing the left uterine artery for hemostatic reasons, the rudimentary horn with one cavity was resected. Guided by vaginal ultrasonography we then completely resected the second cavity located deep in the myometrium without entering the cavity of the functioning hemiuterus. Finally the uterine defect was sutured in two layers. Surgery and postoperative course were uneventful. At 4-month follow-up, dysmenorrhoea was alleviated, and 3 months later the patient had an early intrauterine pregnancy. We believe the precise dissection capabilities of the robot facilitated in particular resection of the second, deeply located cavity and its multilayer reapproximation by sutures. A video of the procedure is provided.