Purpose: The purpose of this study was to test the reliability and validity of an instrument to measure suffering of family of patients with terminal cancer. Methods: This research was a methodological study processed as follows: 1) The preliminary 32 items were developed based a conceptual framework of suffering for patients with cancer. 2) The content was validated by an expert panel (n=24) and the family of patients with terminal cancers (n=33). 3) The instrument was validated by survey (n=92). Finally, 29 items were selected in developing final version of the scale. Results: Seven factors were extracted through factor analysis: ‘economical distress’, ‘loss of meaning in life’, ‘feeling of social isolation’, ‘emotional distress’, ‘burnout’, ‘guilty feeling’, and ‘physical discomfort’. These factors explained 66.94% of the total variance. Cronbach’s alpha and Guttman Split-half coefficient of the 29 items were .93 and .92. respectively. Conclusion: This scale identified as a valid and reliable tool with a high degree of reliability and validity. It can be effectively utilized to assess the degree of suffering of family in palliative care settings.