Background: Although COVID-19 attracted attention to the environments of professional nursing practice, triggering a series of responses to address some of the most pressing problems, it is important to identify the size and scope of other weaknesses that have emerged. Methods: In an observational and cross-sectional study, using the Scale for the Evaluation of the Environment of Professional Nursing Practice, 752 nurses from a Portuguese university hospital, provided socio-demographic and professional data about the components structure, process and outcome of their professional nursing environment. Data collection took place from June 1–30, 2020, immediately after the first critical period of the COVID-19 pandemic in Portugal. Results: In the analysed environment of professional nursing practice, Process factors were favourable to the quality of care, while the Structure and Outcome factors had a moderately favourable effect. Structure factors related to work contexts (P < .001) and nursing functions in patient care areas with COVID-19 (P = .001). Process factors related significantly to work contexts (P < .001). A significant association was found between Outcome factors and work contexts (P < .001) and nursing functions in patient care areas with COVID-19 (P = .005). Conclusion: The environments of professional nursing practice in the hospital under study are moderately favourable to the quality of care. However, the need to invest in nurses’ participation, involvement and professional qualification is clear. Maintenance of a sustainable nursing workforce requires attention to be given to ensuring that practice environments are conducive to the quality of care and geared to promoting professional involvement and job satisfaction among nurses.