Background: Integrated care is an important strategy for improving the process and outcome of healthcare delivery for patients with complex needs. Until now, there has been no universally accepted and validated measurement tool for integrated care. This study aimed to validate The Rainbow Model of Integrated Care Measurement Tool (RMIC-MT) which assesses, using a self-administered questionnaire, micro level (clinical), meso level (professional and organisational), macro level (system) and enabling (functional and normative) aspects of integrated care.Methods: Potentially relevant items were developed on the basis of a literature review and qualitative synthesis process. Three modified Delphi studies were used to asses the content validity of the items. Primary survey data were collected from healthcare providers and managers participating in integrated care projects from The Netherlands, Singapore and Australia. The RMIC-MT was validated for face validity, internal consistency, construct validity and reliability.Results and conclusions: The RMIC-MT is one of the first attempts to systematically measure different aspects of integrated care across the care continuum. Preliminary results suggest that the RMIC-MT is both a reliable and valid tool for assessing integrated care in different integrated care settings. The results of the construct and reliability analysis across countries will be presented, interpreted and discussed.