Reducing nurses' autonomy can impair their decision-making and ability for appropriate interventions. Lowered independence hinders ethical reasoning, which may lead to moral distress. This descriptive correlation study investigates the relationship between professional independence and moral distress in 173 nurses working in emergency departments in Tabriz, Iran. Data were collected using questionnaires designed to assess professional autonomy and moral distress and analysed using descriptive and inferential statistics via the SPSS 13 software. The level of professional autonomy among emergency nurses was low (83.2±16.9), and moral distress, moderate (7.43±3.52). A statistically significant negative relationship was reported between professional independence and the frequency of moral distress (p=0.018). Bivariate analysis related professional autonomy with the frequency and intensity of moral distress. Multiple regression analysis showed that age significantly predicted moral distress (frequency, intensity, and total scores). Lack of autonomy hinders nurses from functioning effectively and efficiently in practice and even can lead to moral distress. Increasing professional independence and the use of experienced nurses as mentors in emergency settings to support younger nurses can help with the reduction of moral distress.