Early prediction of future acetabular development is important to determine an additional surgery for developmental dysplasia of the hip (DDH). The purpose of this study was to investigate the predictive factors of acetabular development using MRI. We retrospectively investigated dislocated 40 hips and 34 normal hips in 37 pediatric patients (9 males and 28 females) with DDH who underwent open reduction after walking age. We evaluated the cartilaginous acetabulum and labrum of the patients using coronal MRI T2*-weighted images at 5 years of age. The mean age at the time of surgery was 22 months, and the mean age at the final survey was 19 years. We divided patients into two groups in accordance with the Severin classification at the final follow-up. Groups with good outcomes (affected 26 hips and unaffected 27 hips) and poor outcomes (14 hips and 7 hips) were compared using the MRI parameters on each side. Predictive factors of acetabular development were identified using univariate and multiple logistic regression analyses. Using multiple logistic regression analysis, labral acetabular roof depth and labral hip center distance at 5 years of age represented predictors after open reduction (odds ratio 0.27, P = 0.035; odds ratio 3.4, P = 0.028, respectively) on the affected side, and bony hip center distance represented a predictor on the unaffected side (odds ratio 2.6, P = 0.049). Acetabular development in the unaffected side could be predicted by bony assessment, while acetabular development in the affected side had to be assessed by labrum using MRI.