Purpose: The purpose of the present study was to develop a Dietary Habit Self-Management Skill (DHSMS) scale, and to test the reliability and validity of this scale. Methods: A questionnaire survey was then conducted using a 69-item DHSMS scale (second draft) for which content validity had been confirmed. The participants were post-gastrectomy cancer patients aged from 40 to under 80 years who had undergone initial gastrectomy with an interval of from 1 month since discharge to <3 years post-operative. Results: The scale is a second-order factor model with "Dietary habit self-management skills" as a higher-order factor, four factors-"Skill to form partnerships with other important people", "Skill to prevent or cope with post-gastrectomy disorder", "Skill to grasp issues accompanying post-gastrectomy disorder", and "Self-efficacy"-and 27 items. The construct validity of the scale was confirmed. Cronbach's alpha coefficient of the DHSMS scale was 0.915. The criterionrelated validity of the DHSMS scale was confirmed based on the correlations between overall DHSMS scale scores and "Number of post-gastrectomy disorder symptoms experienced", the score for the subscale "Skill to grasp issues accompanying post-gastrectomy disorder" and "Number of post-gastrectomy disorder symptoms experienced", and the subscale "Self-efficacy" and the SF-8. Discussion: By using patients' self-administered DHSMS scale scores, medical professionals are able to assess the level of a patient's self-management skills and the status of their dietary habits as a result of post-gastrectomy disorder.