Intensive care units (ICUs) provides intensive treatment medicine to avoid complications such as malnutrition, infection and even death. As very little is currently known about the nutritional practices in Iranian ICUs, this study attempted to assess the various aspects of current nutrition support practices in Iranian ICUs. We conducted a cross-sectional study on 150 critically ill patients at 18 ICUs in 12 hospitals located in 2 provinces of Iran from February 2015 to March 2016. Data were collected through interview with supervisors of ICUs, medical record reviews and direct observation of patients during feeding. Our study showed that hospital-prepared enteral tube feeding formulas are the main formulas used in Iranian hospitals. None of the dietitians worked exclusively an ICU and only 30% of patients received diet counselling. Regular monitoring of nutritional status, daily energy and protein intake were not recorded in any of the participating ICUs. Patients were not monitored for anthropometric measurements such as mid-arm circumference (MAC) and electrolyte status. The nasogastric tube was not switched to percutaneous endoscopic gastrostomy or jejunostomy (PEG/PEGJ) in approximately 85% of patients receiving long-term enteral nutrition (EN) support. Our findings demonstrated that the quality of nutritional care was inappropriate in Iranian ICUs and improvement of nutritional care services within Iranian ICUs is necessary.