Mechanical ventilation is a lifesaving modality in critically ill patients. It is achieved through passage of Endotracheal Tube in the trachea for the assistance in breathing and removal of tracheal secretions. ETT tends to interfere in the function of mucociliary ladder putting the patient at risk for accumulation of secretions which requires an utmost need for endotracheal suctioning. This invasive procedure ensures the patency of ETT and deliverance of adequate oxygenation to the patient, but lack of knowledge and malpractices of the nurses tends to put the patient at risk for certain complications. The study was aimed to evaluate the effectiveness of structured training program in enhancing performance knowledge of ICU nurses in terms of ETT suctioning. For the evaluation of knowledge and skill, a questionnaire and observational checklist was developed along with the protocol of ETT suctioning in the context of evidence based guidelines. Quasi experimental design was chosen with purposive sampling technique. The sample size was 50 students of Post Basic Diploma in ICU/CCU from various college of nursing of Lahore and Islamabad. Findings of the study proposed that post implementation knowledge and practices of ICU nurses were immensely improved with p value of 0.00, respectively. Henceforth, the structured training program proved to be promising and had a meaningful influence to enhance the performance knowledge of ICU nurses in relation to ETT suctioning guidelines.