Background: Nursing workforce capacity, competency, and practice environments are widely recognized as critical determinants of healthcare quality and system performance. Persistent challenges such as staffing shortages, skill-mix imbalances, increasing workload, and unsupportive organizational climates continue to threaten patient safety, care quality, and workforce sustainability worldwide. Despite a growing body of empirical research, evidence remains fragmented across these workforce dimensions.

Objective: This systematic review aims to synthesize and integrate existing evidence on the impact of nursing workforce capacity, professional competency, and practice environments on healthcare quality and performance outcomes.

Methods: A systematic review was conducted in accordance with PRISMA guidelines. Peer-reviewed studies published in English were retrieved from major databases, including PubMed, Scopus, Web of Science, and CINAHL. Eligible studies examined relationships between nursing workforce variables and patient-, organizational-, or system-level outcomes. Data were extracted and synthesized narratively.

Results: The evidence consistently demonstrates that adequate nurse staffing, higher levels of clinical competency, and supportive practice environments are associated with reduced mortality, fewer adverse events, improved patient satisfaction, enhanced efficiency, and better workforce retention.

Conclusion: Strengthening nursing workforce capacity, investing in competency development, and improving practice environments are strategic priorities for achieving sustainable improvements in healthcare quality and system performance.