Purpose: The aim of this study was to develop a measurement tool to assess health-related behavior of adolescents with moyamoya disease. Design: This was a methodological study to develop and validate the Moyamoya-Health Behavior scale (Moyamoya-HB scale) for adolescent patients. Methods: The initial 108 items of the preliminary Moyamoya-HB scale for adolescent patients were generated based on extensive literature reviews and in-depth focus-group interviews with eight moyamoya-suffering adolescents and 12 parents. Group interviews were conducted by six experts (two pediatric neurosurgeons, one psychologist and three nurses). Psychometric testing was performed with a convenience sample of 120 hospitalized adolescents with moyamoya disease recruited from Y University hospitals in South Korea. The construct validity, convergent validity and discriminant validity were tested by exploratory and confirmatory factor analysis. For criterion validity, concurrent validity was confirmed by using the Korean adolescents’ health behaviors tool. To confirm the reliability of the Moyamoya-HB scale, the construct reliability and Cronbach’s alpha coefficients were calculated. Findings: The final 12-item Moyamoya-HB scale for adolescents was categorized by three sub-domains: implementation of treatment for moyamoya disease, health promoting behavior for moyamoya disease and health coping behavior for moyamoya disease. Overall, these factors explained 68.97% of the total variance. The result of the confirmative factor analysis supported the construct, convergent and discriminant validity of the three sub-domains. The Moyamoya-HB scale for adolescents also demonstrated a concurrent validity with the Korean adolescents’ health behaviors tool ( r = .59, p <.001). Reliability analysis showed an acceptable-to-high Cronbach’s alpha of .865 in total, and the subscales ranged from .800 to .841. Conclusion: The Moyamoya-HB scale is a valid and reliable instrument for evaluating the awareness of hospital safety among hospitalized children . Clinical relevance: The Moyamoya-HB scale should be able to contribute to building empirical- and evidence-based data for the development and application of various intervention programs for health promotion of adolescents with moyamoya disease and the prevention of hospital-related accidents among children.