Background: Total hip arthroplasty (THA) is a surgical technique to correct developmental dysplasia of the hip (DDH). Various THA-based methods have been developed for managing end-stage osteoarthritis in patients with DDH Crowe type III or IV. Objectives: In this study, we evaluate the Harris hip score (HHS) before and after cementless THA without subtrochanteric shortening osteotomy (STO) in patients with DDH Crowe type III or IV who were candidates for THA, as well as complications and the need for revision surgery. Methods: This retrospective cohort study was conducted on patients with DDH Crowe type III and IV, who were candidates for cementless THA using the Watson Jones technique without shortening STO. The HHS was calculated and recorded in their medical files before surgery. Patients with missing or incomplete medical files, without written informed consent, with neurovascular diseases, immunosuppressive drug use, congenital bone and articular anomalies, low back pain radiating to the lower extremities, simultaneous fractures, a history of lower extremity fractures, or joint infections were excluded. The HHS was recalculated during outpatient follow-up. Neurovascular defects and the need for reoperation were also evaluated. All data were recorded and analyzed. Results: Thirty-two patients were enrolled with a mean ± SD age of 50.34 ± 15.45 years, most of whom were women (75%). The patients were followed for 2 to 7 years. Postoperative nerve defects were observed in only 1 (3.1%) patient. Hip reoperation was performed in 1 (3.1%) patient. The mean ± SD of HHS before surgery was 50.10 ± 12.48, which increased significantly to 77.99 ± 15.60 after surgery (P < 0.001). Furthermore, the HHS was evaluated before and after the intervention for each gender, showing a significant increase in both. Conclusions: Cementless THA without shortening osteotomy can improve HHS in patients with DDH Crowe III and IV, providing satisfactory outcomes. Furthermore, complications, such as neurological defects and the need for reoperation, are minimal with this method.