Introduction: The difficulties in the management of the blunt chest wall trauma patient in the Emergency Department due to the development of late complications are well recognised in the literature. The first aim of this study was to investigate the risk factors for the development of complications following blunt chest wall trauma. Using these risk factors, the second aim was to develop and validate a prognostic model that can be used to assist in the management of this patient group. Methods: The risk factors for the development of late complications following blunt chest wall trauma were investigated using a number of methodologies. These included a systematic review and meta-analysis, a questionnaire study and a retrospective observational study. Following identification of the risk factors, a prognostic model was developed using multivariable logistic regression. This model was then externally validated in a prospective multi-centre study. Results: The systematic review, questionnaire study, retrospective study and development study results highlighted that the risk factors for the development of complications following blunt chest wall trauma were an increasing patient age, the existence of chronic lung disease, an increasing number of rib fractures, the use of pre-injury anti-coagulants and a decreasing oxygen saturation level on presentation to the Emergency Department. These risk factors were included in the final model. Results of the validation study indicated an overall model accuracy of 87%, a sensitivity of 75% and a specificity of 97%. A concordance index of 0.96 highlighted an excellent discriminatory ability of the model. Conclusions: The prognostic model developed in this study demonstrated good predictive capabilities in the derivation sample and excellent discrimination in the validation sample. The model demonstrates clinical usefulness as it includes risk factors not normally considered in the management of blunt chest wall trauma patients in the clinical setting.