© 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.The present study aims to develop a causal model of nurses’ compassionate competence based on professional self-concept and work conscience and the mediating role of self-efficacy and is considered a descriptive and structural equation modeling. The statistical population of the study includes all nurses working in the psychiatric ward of Ardabil hospitals in 2020. The sample constituted of 200 nurses working in the psychiatric ward selected by purposive sampling and having entry and exit criteria from the statistical population. Data were collected using the Lee and Simon Compassionate Competence Scale, Cowin et al.‘s Professional Self-Concept Questionnaire, the Costa and McCray Work Conscience Questionnaire, and the Scherer and Maddox Self-Efficacy Questionnaire. Following that, the data were examined using structural equation modeling (SEM). Based on the results, the causal model of the relationship between professional self-concept, work conscience, self-efficacy, and compassionate competence of nurses was confirmed according to different fit indices. Professional self-concept, work conscience, and self-efficacy directly affect nurses’ compassionate competence. Moreover, professional self-concept and work conscience through self-efficacy indirectly affect nurses’ compassionate competence (P < 0.05). Therefore, professional self-concept, work conscience, and self-efficacy play an essential role in the level of compassionate competence of psychiatric nurses and targeting these three components by psychological therapies can effectively improve the compassionate competence of psychiatric nurses.