This study develops a scale that assesses the self-efficacy of Sri Lankan nursing educators in assuming the roles of nursing educators and validates its psychometric properties. This methodological research followed the DeVellis Scale Development Model, which involves six steps of instrument development and evaluation. Preliminary items were determined through a literature review and focus group interviews with nine Sri Lankan nursing experts. The experts, comprising five South Korean and two Sri Lankan nursing professors, tested the scale’s content validity. Moreover, 15 nursing educators participated in a pilot study, and 126 educators took part in the main survey. To evaluate the scale’s validity and reliability, the data from a preliminary questionnaire were analyzed using SPSS/IBM and AMOS 24.0. Further, construct validity was tested using exploratory and confirmatory factor analyses, and reliability was tested by calculating Cronbach’s alpha and performing split-half testing. Finally, 39 items under four themes, “clinical mentorship” (18 items), “research” (10), “teaching” (6), and “advising” (5), explained 63.5% of the total variance. Confirmatory factor analysis results revealed an acceptable model fit for the final scale. The developed scale achieved a Cronbach’s alpha value of 0.97. Thus, the psychometrical properties of the scale measuring Sri Lankan nursing educators’ self-efficacy were comprehensively evaluated and found acceptable. The developed scale will be useful in guideline development or studies regarding the self-efficacy of nursing educators’ roles in developing countries with similar context to Sri Lanka.