The aim of this study was to assess the correlation between the occurrence of iatrogenic ulnar nerve injury and frontal and saggital angular insertion of the medial pin in type 3 pediatric supracondylar humerus fractures treated by closed reduction and percutaneous fixation using a cross-pin configuration. Radiographs of 90 children were retrospectively reviewed and two radiographic parameters were measured. The frontal humerus-pin angle was formed between the long axis of the humerus shaft and the axis of the medial pin on an anteroposterior radiograph. The saggital humerus-pin angle was formed between the long axis of the humerus shaft and the axis of the medial pin on a lateral radiograph and expressed as positive and negative values if the insertion direction of the pin was anterior to posterior or posterior to anterior, respectively. There was a significant difference between the mean saggital humerus-pin angle values of ulnar nerve injury and no neurological complication groups (12.1 degrees versus 1.6 degrees , respectively; P=0.001). It was concluded that, anteroposterior insertion of the medial pin in the saggital plane, while the elbow was in hyperflexion, correlated with the occurrence of iatrogenic ulnar nerve injury.