The present case report defines a rare case of a liposarcoma with bone metastasis resulting in a complete remission (CR) following trabectedin treatment. The patient was referred with abdominal swelling and pain. A retroperitoneal mass was detected and described as dedifferentiated liposarcoma (DDLS). The mass was surgically removed and consequently adjuvant chemotherapy was administered. Three months after the completion of chemotherapy, patient presented with bone metastasis in thoracic and lumbar vertebrae. Vertebroplasty and radiotherapy (RT) was performed. After these therapies, bone pain persisted and bone scintigraphy showed increased activity in L4, T11, and T12 vertebrae. Zoledronic acid was added to trabectedin treatment. CR has been detected on bone scintigraphy and positron emission tomography-computed tomography (PET-CT) after 18 weeks. Previous cases about liposarcoma treated with trabectedin were mostly about the myxoid/round cell type (former name, currently known as myxoid liposarcoma (MLS)) and mostly reported partial responses. In this study, trabectedin was used for the treatment of a metastatic retroperitoneal DDLS and a CR was achieved.