Nurses' work environment influences nursing practice. Inappropriate working conditions are the result of underdeveloped workplace infrastructure, poor work organisation, inadequate education, and inappropriate staffing norms. The aim of this study was to describe and examine the predictors that affect nurses' work environment using the Practice Environment Scale of the Nursing Work Index (PES-NWI). The validation of the PES-NWI was made. Nurse-reported job characteristics were used as independent variables. The sample included 1,010 nurses from adult surgical and medical units at 10 Slovenian hospitals. The Nurse Forecasting (RN4CAST) protocol was used. Permission to conduct the study was obtained from the National Medical Ethics Committee. The PES-NWI mean (2.64) was low, as were job and career satisfaction at 2.96 and 2.89, respectively. The PES-NWI can be explained in 48% with 'Opportunities for advancement', 'Educational opportunities', 'Satisfaction with current job', 'Professional status', 'Study leave', and 'Level of education'. A three-factor solution of PES-NWI yielded eight distinct variables. The obtained average on the Nursing Work Index was one of the lowest among previously conducted surveys. Nurses should be recognized as equals in the healthcare workforce who need to be empowered to develop the profession and have career development opportunities. Inter-professional relations and equal involvement of nurses in hospital affairs are also very important. This is a non-intervention study - retrospectively registered.