BackgroundPatient participation is advocated in various healthcare settings. Instruments for assessment and feedback have been developed to strengthen clinician-patient interaction. In an emergency department context, such instruments are still missing.The study aimed to develop and test an observation tool for emergency teams’ behaviour regarding patient involvement and collaboration.MethodsThe development of the behavioural observation tool followed a systematic approach. The tool’s content was based on various data sources, i.e., published literature, interview and observational data, and expert consensus. An international expert panel reviewed the content and the rating scale and rated its importance for patient involvement and collaboration in a Delphi process. The feasibility and reliability of the tool were tested by trained observers using video recordings of simulated emergencies. Intraclass correlation (ICC) and Kappa-statistics were performed to test the tool’s inter-rater reliability.ResultsThe PIC-ET tool, a 22-item observation instrument was developed in which patient involvement and collaboration behaviours are rated from ‘no’ to ‘high’ using behavioural anchors. Expert agreement was obtained after three Delphi rounds on the tool content, the behavioural anchors and its importance for patient involvement and collaboration.The content validity was assessed as high, and the tool was found feasible for research. Overall inter-rater reliability was fair (Kappa 0.52).ConclusionsA novel tool for assessing emergency teams’ behaviour regarding patient involvement and collaboration is introduced. The tool’s psychometric properties were fair to good. Further validation of the PIC-ET tool is recommended for more robust evidence. Future adaptation to different contexts and areas of use, as well as further validity testing may be of value.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12873-023-00841-7.