Background: Caring for critically ill patients with chest drain is an essential part of nursing practice so that, nurses must be equipped with appropriate knowledge and skills to meet the needs of such group of patients safely and competently. Aim: This study aims to assess the effect of educational guidelines on nurses' performance for caring of critically ill patients with digital chest drainage system. Design: A quazi experimental design was utilized. Setting: At cardiac intensive care unit & chest intensive care unit which affiliated to Ain Shams University Hospital at Cairo - Egypt. Sample: A purposive sample of 60 nurses caring for patients with digital chest drainage system in the previously mentioned units were be recruited in the current study. Tools: Two tools were be used to collected 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: Less than three quarter of nurses had total unsatisfactory level of performance regarding caring for critically ill patients with digital chest drainage system pre the educational guidelines implementation. Meanwhile the majority of the study sample had statistically significant improvement in their performance post the educational guidelines implementation. While this improvement lowered slightly post- implementation by follow up. Conclusion: The educational guidelines for nurses was effective in improving their performance regarding caring for critically ill patients with digital chest drainage system. Recommendations: Implementing the educational guidelines on a wider field including all governmental hospitals is necessary to raise the efficiency of nursing care given for patients with digital chest drainage system.