Self-awareness is an essential nursing competency and there is limited knowledge about nurses’ levels and application of self-awareness and instruments to measure nursing-specific self-awareness. Using mixed methods, we developed and tested a scale to measure nurses’ self-awareness. First, 13 nurses were interviewed to understand their meanings of self-awareness and to develop nursing-specific self-awareness scale. Qualitative analysis generated professional, personal, contextual, and contentious aspects of self-awareness. Second, a 25-item scale assessed through expert consultations and pilot testing with 252 nurses. The content validity index was 0.94. After psychometric testing, seven items were deleted. Cronbach’s alpha for the 18-item scale was 0.87 and the four-factor structure accounted for 45.55% of the variance. Lastly, the final scale was administered to 216 nurses. Nurses’ had moderate self-awareness (59.65 ± 7.01), significantly associated with age and years of the clinical and educational experience. Intensive care nurses were more self-aware than nurses in other settings.