In this thesis it is argued that moral sensitivity is necessary to recognize, interpret and respond appropriately the ethical problems experienced by nurses in Primary Health Care. This study has a Luso-Brazilian perspective insofar as it is part of the double degree agreement between the Universidade Católica Portuguesa and the School of Nursing of the University of São Paulo. The Luso-Brazilian comparison of results makes it possible to absorb from the reality of each country, strategies and ways to increasingly qualify nursing care. This study aims to evaluate the moral sensitivity of nurses working in primary health care in Portugal and Brazil. More specifically, to translate and adapt the moral sensitivity questionnaire for nurses in primary health care in Portugal and Brazil, to validate the questionnaire of moral sensitivity with nurses of primary health care in Portugal and Brazil and to characterize the factors associated with Level of moral sensitivity of nurses in primary health care in Portugal and Brazil. This is a descriptive, cross-sectional, observational and correlational study of two independent samples. The sample consisted of 331 nurses from Portugal and 316 nurses from Rio Grande do Sul/Brazil. The Moral Sensitivity Questionnaire Brazilian version (MSQ-B) and Portuguese version (MSQ-P) after validation remained with 27 items, distributed in four dimensions: interpersonal orientation, professional knowledge, moral conflict and moral meaning. The MSQ-B explained 55.8% of the total variance and had a Cronbach's alpha of 0.82. The MSQ-P presented a variance of 54.0% and a Cronbach's alpha of 0.89. The mean of moral sensitivity of nurses in primary health care in Rio Grande do Sul/Brazil was 4.49 and in Portugal was 4.94 of 7. The moral sensitivity questionnaire is a valid and appropriate instrument to evaluate the moral sensitivity of nurses in Rio Grande do Sul/Brazil and Portugal. The study observed all ethical and legal precepts of research involving human beings, since it guarantees a free and voluntary participation. The research is developed under the modality of full doctorate abroad, granted by the Coordination for the Improvement of Higher Education Personnel-CAPES.