Background: Autonomy is a major element of professional practice in nursing and an important factor in improving the quality of patient care. This study aimed to design and validate a questionnaire to assess the professional autonomy of clinical nurses.

Methods: This study utilised an exploratory sequential design in three stages. In the first stage, the constructive themes of the concept of nurses' professional autonomy were determined using a meta-synthesis. In the second stage, semi-structured individual interviews were conducted with 19 nurses, and analysis was performed using the deductive content analysis method. Finally, a methodological study was conducted to design and validate the clinical nurses’ professional autonomy questionnaire by testing for face, content, and structural validity. Reliability of the questionnaire was calculated by examining internal consistency and stability.

Results: Based on the first and second stages, the initial pool of the questionnaire of 99 items was designed. The content validity index for the entire questionnaire was 0.964. For exploratory factor analysis, 250 nurses were included using the convenience sampling method. Varimax rotation and maximum likelihood methods were used to extract the factors. Finally, the clinical nurses’ professional autonomy questionnaire with 31 items and seven dimensions including "professional care", "professional mutual respect", "professional decision making", "leadership role", "professional discipline", "clinical skills" and "critical thinking" was developed with a 5-point Likert scale. The reliability was confirmed by Cronbach's alpha coefficient of 0.885, and the stability was confirmed by the intra-cluster correlation coefficient of 0.840.

Conclusions: According to the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) criteria, the present questionnaire has desirable psychometric properties and is the first questionnaire specifically designed in Iran to assess professional autonomy in clinical nurses with applicability in different clinical departments.