There is consensus that a professional full-time nursing workforce leads to better patient outcomes and a safer health care environment. In 2007, the Ontario Ministry of Health and Long-Term Care introduced the Nursing Graduate Guarantee (NGG), a policy mechanism designed to strengthen the nursing workforce by increasing full-time (FT) employment for newly graduated nurses. Several factors have affected the supply and employment status of nurses in the province over the past two decades, including the introduction of unregulated health care workers and crises such as SARS and COVID-19. A secondary analysis of the College of Nurses of Ontario registration database was conducted to identify and evaluate trends in the supply and employment of nurses in Ontario prior to and following introduction of the NGG. The results demonstrate that full-time employment of new registered nurses and new registered practical nurses initially increased but has since fallen to below pre-policy levels. Part-time work among newly graduated nurses is increasing across all sectors, signaling a diminishing effect of the NGG investments over time. Investments in health human resources have a stabilizing effect on the nursing workforce. Ensuring an adequate number of nurses is necessary for crisis preparation, management and recovery, particularly in sectors with low surge capacity such as long-term care. However, sustained financial, political, public, and professional support is required.