Background: The duration of mechanical ventilation (MV) is one of the most important clinical factors which predict outcomes in pediatric cardiac surgery. The prolonged mechanical ventilation (PMV) following cardiac surgery is a multifactorial phenomenon and there are conflicts regarding its predictors in pediatric population between different centers. Objectives: The current study aimed to describe PMVpredictors in patients undergoing cardiac surgery for congenital heart disease in a tertiary center for pediatric cardiovascular diseases in Iran. Patients and Methods: From May to December 2014, all pediatric patients (less than a month -15 years old) admitted to pediatric Intensive Care Unit (PICU) after congenital heart surgeries were consecutively included. The PMV was defined as mechanical ventila- tion duration more than 72 hours as medium PMV and more than seven days as extended PMV. The demographic data and variables probably related to PMV were recorded during the PICU stay. Results: A total of 300 patients, 56.7% male, were enrolled in this study. Their mean age was 32 ± 40 months .The median duration (IQR) of MVwas 18 hours (8.6 - 48 hours). The incidence of PMV more than 72 hours and seven days was 20% and 10.7%, respectively. Younger age, lower weight, heart failure, higher doses of inotropes, pulmonary hypertension, respiratory infections and delayed sternal closure were independent predictors of PMV in multivariate analyses. Conclusions: The results of this study indicated that PMV predictors could be specific for each center and a good administration program is needed for each pediatric cardiac surgery center for the preoperative management of patients undergoing congenital heart surgeries.