Wide tumor resection is the local treatment of choice for patients with primary malignant bone tumors and a prerequisite for long-term survival. We present two patients that underwent total bone resection in the upper limb because of primary malignant bone tumors. The defects were then reconstructed by a 3D printed prosthesis, a procedure that, to our knowledge, has not been reported for bone defects of the upper extremity so far. Complete resection of the affected bone was required in a five-year-old girl with a high-grade osteoblastic osteosarcoma of the humerus and a 53-year-old man with a dedifferentiated leiomyosarcoma of the radius, due to the tumor’s extent. Following neoadjuvant chemotherapy, resection of the entire affected humerus including the axillary nerve took place in the first case and the entire affected radius including parts of the radial nerve in the second case. Approximately three years after surgery, both patients are alive and pain-free. Despite a postoperative drop hand that affected the now 56-year-old man, he is able to carry out everyday activities such as brushing his teeth, writing, and eating. The now eight-year-old girl is also able to engage in normal activities with her left arm such as eating and carrying lightweight objects. Both patients are tumor-free to date.