Leiomyosarcomas represent the most common variant of uterine sarcomas, and are also considered to be the least chemosensitive. To date, adriamycin and ifosfamide are believed to be the most effective drugs for its treatment, in addition to docetaxel and gemcitabine. Recently, the introduction of trabectedin has provided clinicians with another treatment option, and the drug may have some benefits for patients as it may allow for long-term treatment. We present the case of a patient who previously failed multiple cycles of chemotherapy and who was subsequently treated with 30 cycles of trabectedin as third-line therapy for multiple metastases of uterine leiomyosarcoma. During the treatment period, the dosage and dose interval of trabectedin were optimized because of the appearance of grade 4 hematological and gastrointestinal toxicity. Dose adjustments led to acceptable tolerability. Trabectedin was associated with a very good partial response, especially at the pulmonary and pancreatic levels, and stable disease was achieved at all metastatic sites. The patient is currently continuing treatment with trabectedin and has clinically stable disease after 2 years of therapy. This case report provides further evidence that trabectedin is a valid and well-tolerated therapeutic option that can be used in the long term in uterine leiomyosarcoma.