Introduction Although registered nurses (RNs) are central in patient care, we have not found prior research that specifically addresses how RNs assess the safety of patient care at their workplace and how factors in RNs’ work environment are related to their assessments. This study aims to address these issues.

Methods 9236 RNs working with inpatient care in 79 acute-care hospitals in Sweden completed a national population-based survey, including Practice Environment Scale of the Nursing Work Index—Revised and items from Agency for Healthcare Research and Quality's Hospital Survey on Patient Safety Culture. Correlation coefficients (Pearson and Spearman) and proportional odds regression were used for analysis.

Results Nursing work environment factors were strongly related to RNs’ assessments of patient safety. RNs’ perception of having adequate staffing and resources improved their assessment of patient safety by at least two and a half times (OR 2.74 CI 2.52 to 2.97). RNs with a higher level of involvement in direct patient care gave a better patient safety grade than RNs with a more supervisory role. Most, but not all, patient safety culture items were related to RNs’ assessed patient safety grade. We found that work experience seemed to have no influence on RNs’ patient safety assessment.

Conclusions While previous research emphasises patient-to-nurse ratios in strengthening patient safety practices, this study complements this by emphasising RNs’ own perception of having enough staff and resources to provide quality nursing care, as well as having good collegial nurse–physician relations and the presence of visible and competent nursing leadership—all factors highly related to RNs’ assessment of the safety of patient care at their workplace.