Background: Nurses play a vital role in maintaining and promoting quality care, while documentation is the evidence that displays nurses' performance. To achieve set goals regarding patient safety, it is pivotal to keep the clinical record of the patient to understand the patient's overall profile of delivered and intended care and provide the best possible care to improve patient safety through proper and accurate documentation Aim of the study: The study aimed to assess factors influencing effective documentation and its relation to patients' safety as perceived by staff nurses. Study design: A descriptive correlational research design was utilized to fulfill the aim of study. Setting: The present study conducted at Critical Care Units at Benha University Hospital, Qalyubia, Egypt. Subject: The study subjects included all available (420) staff nurses who were working in the above-mentioned study setting. Tools of data collection: Two tools were used in the study first tool: Factors Influencing Effective Documentation Questionnaire, second tool: Patient Safety Questionnaire. Results: The highest factor influencing effective documentation was nurses related factors followed by factors related to nursing administration while the lowest factor was related to work environment, more than two thirds(68.3%) of staff nurses reported that level of patient safety was high. Conclusion: There was highly statistically significant positive correlation between total factors influencing effective documentation with patient safety. Recommendation: Designing and implementing educational program about nursing care documentation standard and providing critical care nurses training courses regarding patient safety by hospital administration.