Background: Nursing care of eyes is considered a basic nursing intervention in critically ill patients. However, it is sometimes neglected due to the focus on supporting vital body functions. These patients are at great risk of eye disorders as a result of their medical conditions and treatment that can alter the eye protective mechanisms, such as the use of ventilatory support and sedation. Preventing eye problems requires improving the critical care nurses' competency through continuous pre-service education, hands-on experience, and in-service training. Aim:  Assess the effect of eye care clinical guidelines training on critical care nurses' competency and eye complications among critically ill patients. Methods: Interventional research using a pre-post design was used to assess and compare nurses' scores before and after the ECCGs training. A Convenient sample of all nurses (75) who worked in the critical care unit in the Main University Hospital at Alexandria University and agreed to participate in the study was enrolled in the study. In addition, a purposive sample of 100 adult patients who had eligible criteria was included in the study. The data of the current study were collected by using three tools namely “eye care clinical competency questionnaire", “Patient's eye assessment record", and “Superficial ocular surface disorders assessment scales package".  Results: A total of 75 nurses and 100 critically ill patients participated in the current study. The percent scores of post-implementation nurses' eye care knowledge and practice were significantly higher than their pre-implementation scores (p ≤ 0.001) respectively. However, there was no significant difference between the nurses' attitude scores (p 0.147). Additionally, the percent scores of eye complications were 84% in patients who received care from nurses before attending the in-service training compared to 46% of eye complications among the patients who received care from nurses after attending the in-service training with a high significant difference between both studied groups (p <0.001). Conclusion: Implementing ECCGs significantly improved eye care nurses' knowledge, and practice, which contributed to reducing the occurrence of eye complications among critically ill patients.