Background: Compassionate care is emphasized within professional ethics codes for nursing and is a key indicator of care quality. The purpose of this study was to design and assess the psychometric properties of a compassionate care instrument for nurses.Methods: This methodological study was carried out in two qualitative and quantitative phases from February 2016 to October 2018. The first phase was composed of a qualitative study using a content analysis approach to explain the concept of compassionate care through interviewing nurses, patients and family caregivers. The original draft of the questionnaire was developed using qualitative findings and a subsequent review of literature. In the second phase, the psychometric properties of the questionnaire were assessed for validity and reliability. Data analysis was performed using descriptive and inferential statistics via SPSS v.16 software.Results: According to the results of the qualitative phase and review of literature, 80 items were extracted. In the quantitative phase, face and content validity led to retaining 40 items. In construct validity, 28 items with a factor load above 0.4 were retained. Convergent validity showed a moderate correlation coefficient between the questionnaire and the nurses' caring behaviors tool (r = 0.67, P = 0.01). Reliability of the 28-item questionnaire using the calculation of the Cronbach's alpha coefficient and the intra-class correlation coefficient were reported as 0.91 and 0.94 for the whole questionnaire, respectively.Conclusion: The questionnaire had an appropriate validity and reliability for measuring nurses' compassionate care. Therefore, the instrument can be used to measure and report the quality of nursing care.