Background: Hypocalcemia may be present as an asymptomatic laboratory finding or as a severe life-threatening condition. Objective: The study aimed to estimate incidence rate of hypocalcemia and to identify risk factors associated with hypocalcemia in patients of Surgical Intensive Care Unit of Zagazig University Hospitals. Patients and methods: This study involved 310 patients who enrolled to Surgical Intensive Care Unit, Zagazig University Hospitals over a period of six months. Total serum calcium concentration and ionized calcium concentration were measured. Results: The distribution of the studied cases according to admission diagnosis, 40% of the studied cases were admitted to ICU due to sepsis and septic shock, 16% polytrauma, 10% respiratory failure, 10% post-operative monitoring, 6% with ICH, 6% with uncontrolled HTN, 4% with ischemic stroke, 2% pancreatitis, 2% dehydration and electrolyte imbalance, 2% DKA and one case due to organophosphorus poisoning and 1% rhabdomyolysis. There was statistically significant negative correlation between GCS score and Ca total and ionized at 3rd day. However, a statistically significant positive correlation was detected between Ph and Ca total at 3rd day.Only sepsis, septic shock, hypertensive crisis, aminoglycosides, respiratory failure and APACHE score were significant risk factors for hypocalcemia. Conclusion: Hypocalcemia is more common in cases with sepsis and septic shock, hypertensive crisis, respiratory failure and cases with electrolyte disturbance.