Since teachers are the closest and most accessible people to students in the school environment, they should be able to apply first aid (FA) intervention correctly and entirely to students who encounter accidents or health problems. In this context, developing valid and reliable tools to measure the FA knowledge of teacher candidates who will be future teachers is of great importance in determining the current situation and shedding light on solutions. This study aims to develop a valid and reliable scale prepared by the content of the three-year certified FA education of the Ministry of Health to measure the FA knowledge of teacher candidates. The population of the study consisted of active students (N=3200) in a total of 16 Teaching Programmes in Muğla Sıtkı Koçman University Faculty of Education and Faculty of Sport Sciences. In this context, 646 teacher candidates who volunteered and completed the data collection tool in the spring semester of the 2023-2024 academic year were reached using the one-stage cluster sampling method (n=646). The study used the FA Knowledge Scale developed by the researchers as a data collection tool. The scale passed through content validity, pilot application, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and reliability analysis, reaching its final form of 19 items. SPSS 27.0.1 and AMOS 25.0 programs were used for data analysis. To test the construct validity of the draft scale obtained from the pilot study, EFA was applied to the first half of the sample group and CFA to the other half. As a result of EFA, it was determined that the scale consisted of 4 factors, which explained 48.75% of the total variance. As a result of the CFA, it was confirmed that the 4-factor structure of the scale was compatible. The scale's internal consistency was calculated with the KR-20 coefficient and found to be 86. The sub-dimensions of the scale are "basic life support," "FA in serious trauma types," "common FA situations," and "patient-injured transport techniques." The maximum score that can be obtained from the scale is 19, and the minimum score is 0. The third quartile value (Q3) estimation of the sample group's score obtained from the scale of knowledge of first aid was determined. A score of 11 and above on the scale was accepted as a sufficient level of CLT knowledge. In this context, it was determined that a scale is a measurement tool with proven validity and reliability, consisting of four sub-dimensions and 19 items that can measure prospective teachers' basic first aid knowledge.