Adenomyosis is a benign disease whose symptoms mimic those of uterine leiomyoma. Hysterectomy is the treatment of choice; conservative surgery is difficult to perform and can damage the uterine structural integrity. We report the case of a 36-year-old woman who had difficulty conceiving because of profuse menometrorrhagia. An 84 cm3 uterine tumour was diagnosed on ultrasonography as leiomyoma, and conservative myomectomy was planned. Magnetic resonance imaging (MRI) corrected the diagnosis to focal adenomyosis. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) destroyed a significant part of the tumour. Following an uncomplicated MRgFUS treatment, a non-perfused volume of 33 cm3 was measured. At 6 weeks, the patient experienced a significant reduction in menometrorrhagia and a marked decrease in tumour size (about 50%). She conceived spontaneously and, after an uneventful pregnancy, gave birth at term to a healthy infant via normal vaginal delivery. No structural uterine abnormality was detected after her delivery. This report highlights the difficult diagnosis and new therapeutic considerations of adenomyosis. MRgFUS seems to have the potential to precisely and effectively treat focal adenomyosis without damage to surrounding healthy myometrium, allowing for normal reproduction. Further studies are needed to assess the overall safety and long-term effectiveness of MRgFUS for the non-invasive treatment of adenomyosis.