OBJECTIVES: The Total Parenteral nutrition (TPN) cost estimation is a part of the PharmacoEconomic program at MOH in Saudi Arabia. The study explored the cost calculations of TPN services by using American Model with local cost. METHODS: Simulation including all 6-month 2015 of TPN services for neonates, pediatrics, and adults patients. It was at 300-Bed Hospital (King Salman Hospital) in Riyadh, Saudi Arabia. Physician or Pharmacist Prescribed TPN. The pharmacist reviews and prepared TPN. The nurse administers TPN, and follows up by doctor or pharmacist. TPN prepared through sterile 797 standards and automated compounding facilities. The cost drives from Ministry of Health information database. The cost Model calculated based on variable expenses including personal cost, material and supply cost. Fixed costs including direct cost, non-salary cost, and overhead cost. All cost used US dollar currency and local prices. RESULTS: The total number patients were 112 with 1631 TPN orders. The estimated cost of TPN services for adult per day was (691.3 USD). The estimated cost of TPN services for pediatrics per day was (773.8 USD). The estimated cost of TPN services for neonates was (863.57 USD).The majority of cost came from overhead cost, direct cost, and material and supply in adults TPN; while the personal cost in pediatrics and neonates TPN services. The total estimated annual expenditures of TPN services were (2,772,752.16 USD). The highest budget expenditures from neonates TPN 92.43 % (2,563,075.76 USD), followed by adults TPN 5.4 % (149,320 USD), and pediatrics TPN 2.17 % (60,356.4 USD) CONCLUSIONS: In this Total Parenteral Nutrition cost-estimation for Saudi Arabia the first study at MOH in Saudi Arabia. It is an essential basic element of PharmacoEconomic program and cost calculation of TPN-related health care services.