Background: The most common causes of re-dislocation after open reduction are inadequate exposure and failure to release the obstructing soft tissues inside and around the hip. Methods: This clinical study included 33 consecutive children (34 hips) who underwent a revision surgery after failed open reduction of developmental dysplasia of the hip (DDH). Results: According to the McKay clinical criteria, the results were good in 28 cases (82.4%), fair in 4 cases (11.8%), and poor in 2 cases with re-dislocation (5.9%). Radiological results according to the modified Severin criteria were as follows: 28 hips (82.4%) were identified as category 2 (good), 4 hips (11.8%) category 4 (fair), and 2 hips (5.9%) category 5 (poor). Conclusions: Revision surgery for DDH is demanding and the long-term consequences are usually serious, but stable, concentric reduction should be obtained either at the first or second open reduction by addressing the causes of failure. Failed acetabulum remodeling and technical errors with inadequate soft-tissue release were the most common causes of failure in the primary operation. Based on the results, the outcome of revision surgery after failed open reduction for DDH was good.