Objectives: The present study discusses ethics in building and using applications based on natural language processing in electronic nursing documentation. Specifically, we first focus on the question of how patient confidentiality can be ensured in developing language technology for the nursing documentation domain. Then, we identify and theoretically analyze the ethical outcomes which arise when using natural language processing to support clinical judgement and decision-making. In total, we put forward and justify 10 claims related to ethics in applying language technology to nursing documents. Methods: A review of recent scientific articles related to ethics in electronic patient records or in the utilization of large databases was conducted. Then, the results were compared with ethical guidelines for nurses and the Finnish legislation covering health care and processing of personal data. Finally, the practical experiences of the authors in applying the methods of natural language processing to nursing documents were appended. Results: Patient records supplemented with natural language processing capabilities may help nurses give better, more efficient and more individualized care for their patients. In addition, language technology may facilitate patients' possibility to receive truthful information about their health and improve the nature of narratives. Because of these benefits, research about the use of language technology in narratives should be encouraged. In contrast, privacy-sensitive health care documentation brings specific ethical concerns and difficulties to the natural language processing of nursing documents. Therefore, when developing natural language processing tools, patient confidentiality must be ensured. While using the tools, health care personnel should always be responsible for the clinical judgement and decision-making. One should also consider that the use of language technology in nursing narratives may threaten patients' rights by using documentation collected for other purposes. Conclusions: Applying language technology to nursing documents may, on the one hand, contribute to the quality of care, but, on the other hand, threaten patient confidentiality. As an overall conclusion, natural language processing of nursing documents holds the promise of great benefits if the potential risks are taken into consideration.