Background: Most of critically ill patients are mechanically ventilated, attached to multiple invasive devices, suffering of the disease, and the particularity of treatment. Physical restraints are commonly used in intensive care units to reduce the risk of injury and ensure patient safety. Aim: to assess the relationship between physical restraints and physiological parameters among critically ill patients. Design: a descriptive design was utilized. Setting:  intensive care units in Tanta university hospitals. Subject: A convenient sample of all available nurses (n= 50) and a purposive sample of patients (n=100). Data collection tools: 1. Nurse's self- administered questionnaire, 2. patient's clinical data, 3. Sedation – Agitation Scale (SAS). Results: It was revealed that, 66% of studied nurses had unsatisfactory level of knowledge. There were a highly statistically significant difference regarding patients' physiological parameters between before, during and after physical restraint p=<0.01. Conclusion: It was concluded that, the most of nurses had unsatisfactory level of knowledge regarding physical restraint. There was a positive correlation between total score of patient's physiological parameters and total score of physical restraint (before, during and after). Recommendation: create an environment free from physical restraints, develop training programs, standards, and appropriate follow-up strategies for nurses regarding physical restraint.