Background: The present study aimed to evaluate the efficacy of nursing educational guidelines to enhance competency-based practice among nurses as genetic counselors. Research design: A quasi-experimental design was used. Setting: data were collected from the oncology and outpatient departments at Benha university Hospital, Qaluobia governorate, Egypt. Subjects: Convenient sample of all available nurses (50) who were working in the oncology and outpatient departments during the data collection period. Tools of data collection: Three tools were utilized to collect data. 1) Structured questionnaires composed of 2 parts: Demographic characteristics and Nurse's Knowledge regarding basics of genetics and genomic, 2) Nurses' attitude toward genetic counseling. 3) Check list to assess competency-based practice among nurses as genetic counselors.  Results: 20% of the studied nurses had satisfactory level of knowledge pre educational guidelines which changed to 94% post guidelines (P<0.05). There were marked improvement in all items of nurses' competency-based practice post educational guidelines with highly statistical difference (P= 0.000).  There were 56% of the studied nurses had positive attitude towards importance of genetic counseling post guidelines implementation compared to 14% pre guidelines implementation (P<0.05). Conclusion: the nursing educational guidelines had significant efficacy on improving the studied nurses' knowledge, practice and attitude regarding basics of genetics and genomic. Recommendations: Incorporate the genetic course into the nursing curriculum and conduct continuous educational interventions to improve the competencies in genetics and genomics among nurses with different degrees and areas of practice.