Background Computer mediated instruction is a technique that offers a plenty arrangement of apparatuses that can be utilized to help an assortment of learning encounters, so the teacher isn't restricted to one lot of administrations or instruments yet can use a few to set up a learning climate which will best suit their understudies' adapting needs. CMI denotes to combination of email, text, audio or video conferencing, instant messaging, list-servers, bulletin boards, and multi-player video games. Settings; this study was carried out at Critical Care and Emergency Nursing Department, Faculty of Nursing- Alexandria University. Method: A quasi experimental research design was used to conduct this study “Tool one: Computer Mediated Instruction Critical Nursing Knowledge test" and “Computer Mediated Critical Nursing Practice checklist". Results: There were statistical significant differences between both groups of students in the favor of study group in relation to nursing knowledge and practice also within the study group after the application of CMI (p < .001). Conclusion: The current study findings concluded that; critical care nursing students who were subjected to computer mediated instruction technique had better knowledge scores and practice performance than those of the control group. Recommendations: it can be recommended that CMI technique should be incorporated in nursing theory and clinical education to improve the level of students' knowledge and clinical practice.