Background: Transverse acetabular fractures often involve the weight-bearing dome of the acetabulum and require precise anatomical reduction for optimal functional recovery. Open reduction and internal fixation (ORIF) using the Kocher-Langenbeck approach remains a preferred method for managing such injuries. This study aimed to evaluate the functional outcomes following ORIF of transverse acetabular fractures using this posterior approach. Methods: This prospective observational study was conducted in the Department of Orthopaedic Surgery at Dhaka Medical College Hospital over 24 months from July 2017 to June 2019. A total of 25 patients aged 21–80 years with radiologically confirmed transverse or associated acetabular fractures were included. All underwent ORIF through the Kocher-Langenbeck approach within three weeks of injury. Functional outcomes were assessed using the Merle d’Aubigné and Postel scoring system at six months postoperatively. Results: The mean age of patients was 36.2 ± 14.12 years, with most (76.0%) between 20–40 years. Anatomical reduction was achieved in 80.0% of cases. At six months, 40.0% of patients had excellent, 20.0% good, 4.0% fair, and 36.0% poor outcomes. Overall, 76.0% had satisfactory outcomes. Pain-free status was observed in 76.0%, normal walking in 76.0%, and 95%–100% hip range of motion in 60.0% of patients. Functional outcome showed a significant distribution difference (p = 0.021), though not significantly associated with reduction quality (p > 0.05). Conclusion: ORIF through the Kocher-Langenbeck approach provides favorable functional outcomes in the majority of patients with transverse acetabular fractures.