Background & aims: A self-efficacy scale for nurses to assess nutritional care of older adults is pivotal for the development of precise educational interventions designed to promote behavioral changes among nurses by enhancing their self-efficacy. However, self-efficacy measurements associated with nutrition care is currently difficult due to the lack of valid and reliable tools. Therefore, this study aimed to develop and validate a self-efficacy scale for nursing nutritional care. Methods: A multi-method and multi-phase design was adopted. Phase one comprised developmental tasks to generate scale items, based on emerging themes in the literature. Phase two comprised the validation, during which its content, construct, and concurrent validity and internal consistency were assessed. For determining construct validity, phase two encompassed two sequential cross-sectional data collection: the first data collection was designed to assess the psychometric characteristics of the scale, whereas the second aimed to confirm the emerging latent structure of the scale. Results: The final version of the developed scale encompassed 27 items, within three domains, including knowledge (regarding nutritional care), assessment and evidence utilization, and care delivery. The scale exhibited evidence of face and content validity, adequate construct and concurrent validity, and good internal consistency. Conclusions: This study resulted in the development of a tool that could be strategically employed for clinical and educational research aimed at improving the quality of nutritional care by enhancing nursing self-efficacy. The developed scale can provide relevant insights for describing nursing competence and its associations with patient-related outcomes.