Abstract: Improvement in health care delivery system requires a deliberate focus on constructing nurses' Quality-Safety Practice Competencies (QSPC) to enhancing their professional growth to provide high quality of patient care and maintain safety. Therefore, it is important to clearly define nurses' QSPC and its attributes (domains) to establish a foundation for an effective health care system. Aim: to develop an instrument for measuring Quality-Safety Practice Competencies for nurses. Methods: a methodological qualitative research design was applied at all hospitals that are affiliated to the Ministry of Health and Population (MOHP), at El-Beheira Governorate, Egypt (n= 20). Subjects: including two groups: (1) panel of experts (n=80), classified into two categories: a) academic experts (n=10) and b) professional experts (n=70); and (2) head nurses and their assistants (n= 350). Tools: two tools were developed, tool one: QSPC Instrument and tool two: pinionnaire sheet. Results: there was highly statistical significant positive correlation between total final version of the developed instrument for measuring QSPC and its attributes (p ≤ 0.01). Conclusion: QSPC instrument has acceptable face validity; excellent content validity and reliability; and construct validity. Recommendations: conducting programs for nursing leaders in different health care organizations to enhance their QSPC; and educating them how to measure nurses' QSPC; measure QSPC for nurses and for newly hiring nurses continuously to evaluate their competencies to addressing the gap in nursing education and practice and find strategies to improve; use Quality-Safety Practice Competencies Instrument as a benchmarking tool to compare nurses' competencies between different departments or between different settings.