Background: Proximal humerus fractures (PHF) should be subject to standardized monitoring during treatment, whether non-operative or operative, to document and adequately assess bone healing. The purpose of this study was to develop a standardized protocol for an image-based monitoring of PHF for joint-preserving treatment options, including a minimum set of descriptors or definitions of features of radiographic images, to be applied in clinical routine practice and studies. Methods: A Delphi exercise was implemented with an international panel of experienced shoulder trauma surgeons self-selected after invitation of all AO Trauma members. Using open questions participants recommended the type and timing of desired diagnostic images, and formulated definitions for the imaging parameters they considered most important. Formulated recommendations for the type and timing of radiological fracture monitoring and clarification of the definitions of the proposed radiological parameter set were subjected to further survey. Consensus for each factor was considered to have been reached when there was at least a two-thirds agreement in the survey participants. Results: Response rates of 231 interested surgeons were 66% and 44% for the first and second survey respectively. Sixty percent of participants to the first survey responded to the second (131/219). 93% of respondents considered radiographic monitoring to be an important part of fracture care. 92% of respondents to the first survey considered that ‘malreduction’ should be assessed, and 165 of 189 respondents provided a suggestion for a definition for this parameter. 88% of respondents to the second survey agreed on a redefinition of the term ‘malreduction’ as ‘non-anatomical fracture reduction’. There was substantial agreement about the radiographic views and orientation of radiographs to be recorded (80%) and the timing of radiological reviews (67- 78% for time points during follow up). Just over half of respondents recommended cessation of radiological review when fracture healing was considered to have occurred by radiological evaluation. Conclusion: Our work confirmed the need for clear definitions of radiological features that should be considered in the follow-up of proximal humeral fractures. It has resulted in the development of an international consensus monitoring protocol for PHF treatment with a structured core set of radiological parameters. Clinical application and validation of the monitoring process are needed.