Background: The international hip dysplasia institute (IHDI) classification is a new method for quantifying the severity of the developmental dysplasia of the hip (DDH). Objectives: This study aimed to compare the reliability of this classification between different medical personnel such as pediatricians, general practitioners, and family doctors in addition to orthopedic surgeons and radiologists. Methods: Hundred pelvic radiographic films (with 200 hips) were randomly selected from the files of children already diagnosed and treated as DDH cases. These films were analyzed by 12 independent observers of four different specialties: three orthopedic surgeons (Ortho Group), three radiologists (Radio Group), three pediatricians (Pediat Group), and three general practitioners (GP Group). Results: The average measures (Cronbach's alpha) for the intraclass correlation coefficient (ICC) for absolute agreement between all observers was 0.874 (with 95% confidence intervals between 0.780 and 0.925). This was considered as having a good level of reliability and agreement between all observers. The ICC for agreement between the observers of radio group showed the highest score (0.904) while that between those of GP Group had the lowest one (0.826). However, during the comparison between the mean score of each group with that of the other groups by the one-way ANOVA method, there was no statistically significant difference between all groups (P values were 0.563, 0.415, 0.399, and 0.291 respectively). Conclusion: The IHDI classification method for cases of DDH has a good level of reliability among different medical personnel regardless of their specialties.