Impacts of the COVID-19 pandemic on the mental health of healthcare workers has been established, linking workplace factors with high levels of stress, anxiety, depression, insomnia and burnout. Less established is how COVID-19 affects both work, home and social life of nurses and midwives concurrently. This study describes the prevalence and severity of anxiety, depression, post-traumatic stress disorder (PTSD) and insomnia and examines their associations with stressors within the work, home and social environment, among nurses and midwives. A longitudinal, mixed-methods, online survey explored the psychological health of public sector nurses and midwives during the COVID-19 pandemic first year. Surveys were conducted in April (initial) and June 2020 (3-month), and April 2021 (12-month) and consisted of psychological tests including the Patient Health Questionnaire, General Anxiety Disorder, Insomnia Severity Index, and the Impact of Events Scale-Revised; workplace and lifestyle questions, together with free-text comments. The relative strengths of the associations between predictor and outcome variables were estimated using repeated measures ordered logistic regression, and free text responses were themed. Data show diagnostic levels of anxiety (23%, 18%, 21%) at surveys one, two and three respectively, depression (26%, 23% and 28%), PTSD (16%, 12% and 10%) and insomnia (19%, 19% and 21%). The strongest predictors of psychological distress were current home and family stress and poor clinical team support. Factors which will help preserve the mental health of nurses and midwives include strong workplace culture, reducing occupational risk, clear communication processes, and supporting stable and functional relationships at home. The COVID-19 pandemic has increased the visibility of mental distress on nurses and midwives and established they are pivotal to healthcare. The health service has a duty-of-care for the welfare of nurses and midwives who have entered this psychologically taxing profession to future proof service delivery and safeguard its service-response capacity.