Background The ipsilateral olecranon with associated radial neck fractures does not include in the Bado classification of Monteggia fractures and equivalent lesions. The primary aims of this retrospective multicenter study were to characterize this type of injury and, noting its unique properties, evaluate the results of the treatment, determine the prognostic factors that influence the radiological and clinical outcome, and also give treatment strategies. Methods Between July 2011 and July 2016, forearm fracture patient charts were retrospectively reviewed from seven pediatric trauma centers. Patients diagnosed with ipsilateral olecranon with associated radial neck fractures and followed up for at least 24 months were included. Fracture characteristics, treatment, outcome, and complications were assessed. The clinical outcome of treatments was evaluated by the Mayo Elbow Performance Score (MEPS) and the Flynn criteria. Fisher's exact test and ANOVA test were used; significance was defined as P < 0.05. Results One hundred thirty-seven consecutive patients (54 girls and 83 boys) from 8292 forearm fractures patients, the mean age of 7.5 years (1.5 to 14.8), with fractures of the ipsilateral olecranon with associated radial neck fractures were identified. One hundred twenty-five patients had radiologic and clinical follow-up. According to a simplified classification system with "operate" and "don't operate" groups, including five subtypes proposed in this study, ipsilateral olecranon with associated radial neck fractures subtypes could be classified with significantly different characteristics and outcome in treatment and complications. Conclusions Fractures of the ipsilateral olecranon associated with the radial neck are not so rare as previously reported. Complications and poor outcomes were easy to encounter without knowing this type of fracture. Appropriate treatment strategies could be made according to a simple classification system based on the treatment result of follow-up.