Objectives: There are several problems and complications related to the Total Parenteral Nutrition (TPN) services. The pharmacist plays a crucial role in preventing these problems. Therefore, in this study, we aimed to assess the economic outcomes of pharmacist intervention in cost avoidance related to TPN services at a public hospital in Riyadh city, Saudi Arabia. Methods: Cohort prospective analysis of data collected regarding pharmacist intervention in TPN services provided to neonates, pediatrics and adult patients was performed. TPN services were provided 8 hr in a day and 7 days in a week. The study site was a 300-bed public hospital at the Ministry of Health (MOH) in Riyadh city, Saudi Arabia. The pharmacist reviews and prepares TPN and he pharmacist documents any or all TPN-related problems before the preparation of TPN or after dispensing it. The pharmacist uses an International Study Model to measure level of activity and provides rational of clinical intervention, recommendation, patient outcome, impact of pharmacoeconomics and related cost analysis. Results: The pharmacist identified a total of 402 TPN-related problems. The total number of TPN services provided was 394 prescribed to 82 patients. Of these, 209 (51.99%) and 193 (48.01%) interventions were provided to males and females, respectively. The total cost avoidance from pharmacist intervention in 1 year was 578,926.89 USD. The highest cost avoidance of TPN interventions was recorded for potentially significant (54.90%; 100,040.91 USD) and potentially serious problems (33.33%; 244,696.83 USD). The maximum cost avoidance in the case of rational clinical activities was recorded for TPN consultations (325,695.76 USD) followed by incompatibility (275,802.66) and inappropriate route (189,912.34 USD). The maximum cost avoidance related to patient outcome was recorded for patient condition improved (489,830.93 USD) and laboratory value improved (89,095.96). The maximum pharmacoeconomic cost avoidance impact was the patient duration of hospital stay decreased (226; 332,220.70 USD) and reduction in the drug therapy monitoring (246,227.15 USD). Conclusion: The clinical pharmacist responsible for TPN services plays an essential role in preventing TPN-related problems and avoid the unnecessary economic burden on the healthcare system. Expanding the role TPN clinical pharmacist is highly recommended for all TPN services to reduce the economic burden on healthcare system in Saudi Arabia.