Quality of life at work  could affect  quality of nursing care and safe practice .Purpose: To assess the quality of work life influence on nurses' competencies in self-assessment.  Research Design: A descriptive correlational study design is used. Setting: Inpatient units in  Kafrelsheikh General Hospital. Instruments: Two instruments were used :(Quality of Work-Life Balance Likert Scale and  Nursing Competency in Self Assessment Likert Scale).  Results: More than half of nurses (63.2%) believed that they lacked certain competencies, and less than half (43%)  had moderate quality of life. Conclusion: There was a highly statistically positive relationship between quality of work life and competencies in self assessment. Recommendations: In order to achieve a high level of competencies for their employees, hospital management must develop healthy environment work. Additional research is required to determine the predictive elements influencing nurses' competencies.