Aim To develop and validate a scale for measuring professional caregivers’ ethical self-efficacy in dementia care. Background Professional caregivers of people with dementia make ethical decisions on a day-to-day basis, and it is important that they feel confident when doing so. Moreover, confidence, or self-efficacy, influences caregivers’ behaviour and well-being and may be a predictor of competence. However, there is no scale for measuring ethical self-efficacy. This study aims to fill this gap. Methods This study concerns the development and prima facie validation of the Dementia-Specific Ethical Self-Efficacy (DemESE) scale. During development, we identified dementia-specific ethical principles and generated items representing ethical conflicts of principles. In the subsequent validation, we administered the scale to experts and professional caregivers in dementia care. We assessed the relevance of the scale using a content validity index and tested validity and reliability using Cronbach’s alpha. To further enhance validity, we compared the scale with analogous self-efficacy scales using Pearson’s correlation coefficient. Results The quantitative testing of DemESE revealed that the scale exhibited acceptable levels of internal consistency and reliability. This finding was supported by Cronbach’s alpha. In addition, the content validity index and Pearson correlation coefficient provided evidence of the scale’s relevance and validity. Conclusion The results suggest that DemESE is a promising tool for assessing professional caregivers’ ethical self-efficacy in dementia care and may be used to measure ethical self-efficacy – that is, confidence in ethical decision-making in dementia care.