Background: In order to determine the extent to which care delivered to children is appropriate (in line with evidence-based care and/or clinical practice guidelines (CPGs)) in Australia, we developed a set of clinical indicators for 21 common paediatric medical conditions for use across a range of primary, secondary and tertiary healthcare practice facilities. Methods: Clinical indicators were extracted from recommendations found through systematic searches of national and international guidelines, and formatted with explicit criteria for inclusion, exclusion, time frame and setting. Experts reviewed the indicators using a multi-round modified Delphi process and collaborative online wiki to develop consensus on what constituted appropriate care. Results: From 121 clinical practice guidelines, 1098 recommendations were used to draft 451 proposed appropriateness indicators. In total, 61 experts (n = 24 internal reviewers, n = 37 external reviewers) reviewed these indicators over 40 weeks. A final set of 234 indicators resulted, from which 597 indicator items were derived suitable for medical record audit. Most indicator items were geared towards capturing information about under-use in healthcare (n = 551, 92%) across emergency department (n = 457, 77%), hospital (n = 450, 75%) and general practice (n = 434, 73%) healthcare facilities, and based on consensus level recommendations (n = 451, 76%). The main reason for rejecting indicators was ‘feasibility’ (likely to be able to be used for determining compliance with ‘appropriate care’ from medical record audit). Conclusion: A set of indicators was developed for the appropriateness of care for 21 paediatric conditions. We describe the processes (methods), provenance (origins and evolution of indicators) and products (indicator characteristics) of creating clinical indicators within the context of Australian healthcare settings. Developing consensus on clinical appropriateness indicators using a Delphi approach and collaborative online wiki has methodological utility. The final indicator set can be used by clinicians and organisations to measure and reflect on their own practice.