Autism Spectrum Disorder (ASD) is a neurodevelopmental condition. Omega-3 fatty acids insufficiency has been linked to ASD. This umbrella meta-analysis was performed to investigate the effects of omega-3 supplementation on clinical manifestations in participants with ASD. Based on PRISMA statement, databases including Web of Science, PubMed, and Scopus were systematically searched for published meta-analyses on the effect of omega-3 supplementation on ASD. To assess the risk of bias, the assessment of multiple systematic reviews (AMSTAR)-2 was utilized. The outcomes were core and non-core symptoms of ASD including social withdrawal/lethargy, cluttering speech, hyperactivity, irritability, and stereotypy. Seven meta-analyses eventually remained in the umbrella review. The results revealed that omega-3 fatty acids supplementation caused a significant reduction in cluttering speech in studies conducted on age ≤8 years (ES= -0.30; 95% CI: -0.55, -0.06; P=0.02). Omega-3 supplementation caused a significant reduction in hyperactivity in participants ≤8 years (ES= -0.30; 95% CI: -0.55, -0.06; P=0.02) and in participants who received the supplements for more than 14 weeks (ES= -0.30; 95% CI: -0.55, -0.06; P=0.02). A dosage of ≤1000 mg/d of omega-3 supplementation led to a significant increase in the stereotypy/ restricted and repetitive interests and behaviors (ES= 0.19; 95% CI: 0.03, 0.35; P=0.02). This umbrella review revealed that omega-3 fatty acid may be a beneficial supplement to control cluttering speech and hyperactivity in children lower or equal to 8 years old with ASD.