Nurses and the environment in which they work have an important role in patient safety and quality of care. Evidence demonstrates a link between lower nurse staffing levels and higher nurse workloads on hospital wards with adverse patient outcomes such as increased mortality, infections, falls and hospital stay, as well as adverse effects on staff well-being. Therefore, ensuring adequate numbers of nurses are on duty and available to care for patients safely has become a crucial task for nurses and hospital managers. In March 2016, Wales became the first country in Europe and one of only a small number of countries globally to legislate on nurse staffing levels. In April 2018, the Nurse Staffing Levels (Wales) Act 2016 was fully implemented in acute medical and surgical hospital wards. This article outlines the background to, and development of, nurse staffing approaches in Wales that preceded the introduction of this legislation. It aims to provide nurses with an understanding of the journey towards introducing legislation for nurse staffing levels and workforce planning in Wales, which will be relevant to those affected by the implementation of any legislation in this important area of healthcare. This article also provides information about how the nurse staffing legislation evolved as a result of important work and collaboration that was already undertaken throughout NHS Wales.