© 2021 Wiley Periodicals LLC.Purpose: The aim of this study is to develop a measurement tool that can be utilized to determine in the psychological first aid application of self-efficacy. Design and Method: The development of scale consisted of the following stages: literature reviews, examination of the conceptual structure, creation of scale items, expert advice, and individual and focus group interviews. Findings: A measurement tool was obtained by factor analysis, consisting of one factor and 35 items. The obtained scales were statistically significant, thereby providing a sensitive measurement (p < 0.05). Practice implications: This measurement tool would assist in determining the self-efficacy of psychological first aid administered by aid providers working in disaster situations, thereby increasing the quality of their intervention.