BACKGROUND: Several studies have indicated that the COVID-19 pandemic has had an impact on nurses' psychological and physical quality of life (QoL), as well as on their professional well-being. The literature also indicates that perceived stress, resilience, social support, the psychosocial work environment and professional identification may be determinants of these variables. However, no studies have examined how these determinants may influence nurses' psychological and physical QoL or professional well-being throughout the COVID-19 pandemic. Thus, this study aimed to investigate the influence the influence of perceived stress, resilience, perceived social support, the psychosocial work environment and professional identification on Portuguese nurses' professional well-being and physical and psychological QoL throughout the COVID-19 pandemic. METHODS: For this longitudinal study, data were collected through self-administered questionnaires focused on QoL, professional well-being, and sociodemographic characteristics. The data collection spanned three distinct time points, from November 2021 to June 2023. Data Analysis was conducted by utilizing random-intercept linear regression models. RESULTS: A total of 555 responses were analyzed at all of the measurement points (340 responses at T0, 122 at T1, and 93 at T2), and compared to those at T0, physical and psychological QoL increased at T2. Perceived stress and support from colleagues diminished at T2 compared to T0. During the COVID-19 pandemic, participants who reported low perceived stress, high resilience, high social support from supervisors, high social support from colleagues, and/or high job satisfaction tended to report greater professional well-being and physical and psychological QoL. CONCLUSIONS: Throughout the COVID-19 pandemic, perceived stress consistently negatively influenced nurses' professional well-being and physical and psychological QoL
moreover, resilience and job satisfaction were consistently significant positive determinants of all outcomes. These insights highlight the need for targeted interventions to reduce stress, enhance resilience, and foster job satisfaction among nurses, thus ultimately improving their QoL, professional well-being and effectiveness in health care delivery, particularly during high-stress periods such as pandemics. Future research should explore how these stressors and protective factors influence nurses' QoL and professional well-being.