To determine whether dietary alpha-linolenic (omega-3) fatty acid intake is associated with lower blood pressure and aortic intima-media thickness (IMT) in people born small for gestational age (SGA). Participants were recruited at age 6 months and followed up every 6-12 months until age 19 years. Blood pressure and food records were assessed at each visit. A total of 1009 participants had at least one blood pressure measure and complete birth weight and gestational age data, including 115 (11%) born SGA (birth weight≤10th percentile). Aortic IMT was assessed by ultrasound at 19 years (n=413). Analysis was by linear mixed models and multivariable linear regression. Children born SGA had greater systolic and pulse pressure from age 14 years onwards. In those born SGA, systolic blood pressure was 2.1 mm Hg lower ([95% CI 0.8-3.3]; P=.001) and pulse pressure 1.4 mm Hg lower ([95% CI 0.3-2.4]; P=.01), per exponential increase in alpha-linolenic acid (ALA) intake; weakened by adjustment for anthropometric measures. Long-term ALA intake was inversely associated with aortic IMT at 19 years in those born SGA (-0.30 mm [95% CI -0.52, -0.08] per exponential greater ALA intake; P=.008), independent of other dietary and anthropometric factors. Long-term dietary ALA intake during childhood is associated with improved vascular health in people born SGA.