This cross-sectional descriptive study was designed to examine critical care registered nurses’ perceptions of nurse-to-nurse incivility and professional comportment, and the extent to which education, nurses’ age, nursing degree, and years of nursing experience is related to their perceptions on these topics. Professional comportment is comprised of nurses’ mutual respect, harmony in beliefs and actions, commitment, and collaboration. Yet, it was unknown whether a relationship existed between a civil or uncivil environment in the nursing profession and nurses’ professional comportment. Correlational analyses were conducted to explore the relationship between perceptions of nurse-nurse incivility and professional comportment, and the relationships between incivility and professional comportment education and perceptions of nurse-nurse incivility and professional comportment. Multiple linear regression analyses were conducted to identify predictors of perceptions of nurse-nurse incivility and professional comportment. Results indicated statistically significant relationships between perceptions of nurse-nurse incivility and professional comportment, and between professional comportment education and perceptions of professional comportment. Professional comportment education was identified as a statistically significant predictor of increased perceptions of professional comportment. Findings of the current study may assist in establishing more targeted and innovative educational interventions to prevent, or better address, nurse-nurse incivility. Future research should more clearly define professional comportment education, test educational interventions that promote professional comportment in nurses, and further validate the Nurse-Nurse Collaboration Scale as a measure of nurses' professional comportment.