BACKGROUND Because patients with advanced cancer live longer, the number of patients with the sequelae of metastatic spine disease has increased. Pathologic instability of the mobile spine has been classified, and minimally invasive surgery has been well described. However, pathologic sacral instability is uncommon and often underdiagnosed. Although most sacral fractures are stable, patients with unstable U- or H-type fractures have spinopelvic dissociation and can experience progressive pain, sacral kyphosis, and neurological injury. Open lumbopelvic fusion carries a high perioperative risk for this patient population, which has often been previously radiated and is medically frail. The authors investigated the utility and safety of percutaneous lumbopelvic fixation, as previously described for traumatic spinopelvic dissociation, in the oncological setting. The authors retrospectively reviewed five consecutive patients with unstable pathologic sacral fractures who had undergone percutaneous lumbopelvic fixation after conservative management failed. OBSERVATIONS Patients experienced significant improvement between pre- and postoperative visual analog scale scores (9.2 and 1.6, respectively) and Eastern Cooperative Oncology Group grades (median 3 and 1, respectively). All patients were independently ambulatory at the final follow-up. Sagittal alignment remained stable in four patients and worsened in one. There were no major medical or surgical complications. LESSONS Percutaneous lumbopelvic fixation shows promising results for palliation, durability, and safety for pathologic sacropelvic instability.