Objective: This prospective cohort study investigated the clinical and radiological efficacy of triangular osteosynthesis (TO) in the management of AO type-B unstable sacral fractures. Methods: All patients with unstable AO type-B sacral fractures were included in this study. They were evaluated clinically and radiologically and underwent TO. Pre- and postoperative clinical parameters included the visual analogue score (VAS) for back pain, Oswestry Disability Index (ODI), and Gibbon classification. Radiological parameters included x-rays and multislice 3-dimensional computed tomography scans of the pelvis and the Tornetta and Matta criteria for fracture reduction. Results: This study included 30 patients (17 males and 13 females; mean age, 31.63±9.65 years). The reported causes of trauma were a fall from height in 17 patients, road traffic accident in 11 patients, and hard objects falling onto the pelvis in 2 patients. According to the AO spine sacral fracture classification system, 8 cases were type B2 and 22 were type B3. At the last postoperative follow-up, the mean VAS improved from 7.77±1.19 preoperatively to 3.97±1.59 (p<0.001), the mean ODI was 15.27±3.34, and the Gibbon classification of cauda equina injury improved from 2.87±0.97 preoperatively to 1.27±0.52 (p<0.001). According to Tornetta and Matta criteria for fracture reduction, the results were excellent (<4 mm) in 73.3% of patients, good (4–10 mm) in 20%, and fair (10–20 mm) in 6.7%. All patients experienced complete fracture healing. Conclusion TO is a less invasive, safe, and effective option for the management of unstable AO type-B sacral fractures with good clinical and radiological outcomes.