Objectives: Endotracheal suction is an invasive airway clearance technique used in mechanically ventilated children. This article outlines the methods used to develop appropriate use criteria for endotracheal suction interventions in mechanically ventilated paediatric patients. Methods: The RAND Corporation and University of California, Los Angeles Appropriateness Method was used to develop paediatric appropriate use criteria. This included the following sequential phases of defining scope and key terms, a literature review and synthesis, expert multidisciplinary panel selection, case scenario development, and appropriateness ratings by an interdisciplinary expert panel over two rounds. The panel comprised experts in the fields of paediatric and neonatal intensive care, respiratory medicine, infectious diseases, critical care nursing, implementation science, retrieval medicine, and education. Case scenarios were developed iteratively by interdisciplinary experts and derived from common applications or anticipated intervention uses, as well as from current clinical practice guidelines and results of studies examining interventions efficacy and safety. Scenarios were rated on a scale of 1 (harm outweighs benefit) to 9 (benefit outweighs harm), to define appropriate use (median: 7 to 9), uncertain use (median: 4 to 6), and inappropriate use (median: 1 to 3) of endotracheal suction interventions. Scenarios were than classified as a level of appropriateness. Conclusions: The RAND Corporation/University of California, Los Angeles Appropriateness Method provides a thorough and transparent method to inform development of the first appropriate use criteria for endotracheal suction interventions in paediatric patients.