Limited pharmacological options are available for management pediatric hypertriglyceridemia. We examined the effectiveness of dietary fish oil supplementation as a means to reduce triglyceride levels in pediatric patients. We reviewed 111 children aged 8 to 18 years with hypertriglyceridemia (≥1.5 mmol/L) undergoing treatment in a specialized dyslipidemia clinic. At the treating cardiologist's discretion, 60 subjects received nonprescription fish oil supplementation (500-1000 mg/d), while the remaining patients did not. Initially there were no baseline differences between groups, including the use of concomitant lipid-lowering medication. Treatment with fish oil was associated with a potential clinically relevant but non-statistically significant decrease in triglycerides and triglyceride-to-high-density lipoprotein (HDL) ratio. Fish oil had no effect on HDL-cholesterol, non-HDL-cholesterol, or total cholesterol. All associations remained unchanged when adjusted for body mass index z score, nutrition, physical activity, and screen time. Fish oil supplementation was not significantly effective in treating hypertriglyceridemia in pediatric patients.