Background Caring for critically ill patients with chest drain is an essential part of nursing practice, especially for those nurses who care for patients with complicated respiratory problems or undergo cardiothoracic surgery.Aim This study aims to assess the effect of an educational guideline on nurses' performance caring for critically ill patients with digital chest drainage system.Methods A quasi experimental design was utilized. At cardiac intensive care unit & chest intensive care unit which affiliated to Ain Shams University Hospital at Cairo - Egypt. A purposive sample of 50 nurses caring for patients with digital chest drainage system in the previously mentioned units were be recruited in the current study. Two tools were used to collect data related to achieve the aim of the present study as following I-Nurses’ knowledge self-administered questionnaire and II-nurses' practice observational checklist.Results Most of nurses had total unsatisfactory level of performance regarding caring for critically ill patients with digital chest drainage system pre the educational guideline implementation. Meanwhile the majority of the study sample had statistically significant improvement in their performance post the educational guideline implementation. While this improvement lowered slightly post 3 months at follow up.Conclusion The educational guideline for nurses was effective in improving their performance regarding caring for critically ill patients with digital chest drainage system. Recommendations: Conducting periodic in-service training advanced care programs for nurses help in improving their performance and quality of care that provided to critically ill patients with digital chest drainage system.