BACKGROUND: Little is known about the effect of fatty acid (FA) concentrations in cord blood on long-term behavioral outcomes. OBJECTIVE: We assessed the effect of FAs in cord blood serum on children's behavioral difficulties at the age of 10 y. DESIGN: A longitudinal study of 416 children from the population-based Influences of Lifestyle-Related Factors on the Immune System and the Development of Allergies in Childhood (LISAplus) birth cohort from Munich was conducted. Individual glycerophospholipid FAs in blood were analyzed in venous cord blood. Data on children's behavior were collected with a parent-reported Strength and Difficulties Questionnaire at 10 y of age. Zero-inflated Poisson regression models were applied and adjusted for sex, parental income, smoking during pregnancy, and dietary intake of arachidonic acid (AA) and DHA at 10 y. RESULTS: A 1% increase in DHA in cord blood serum was found to decrease total difficulties by (exp)β(5)(adj) = 0.93 (SE = 0.02, P < 0.0001) and hyperactivity or inattention by (exp)β(adj) = 0.94 (SE = 0.03, P < 0.04). Higher long-chain (LC) PUFA concentrations in cord blood serum were associated with fewer emotional symptoms [(exp)β(adj) = 0.95, SE = 0.03, P = 0.01], and similarly higher AA concentrations were associated with fewer emotional symptoms [(exp)β(adj) = 0.94, SE = 0.03, P = 0.03]. CONCLUSION: Increased concentrations of DHA, LC-PUFAs, and AA in cord blood serum were associated with lower scores on a parent-completed behavioral screen. An appropriate FA supply to the developing fetus may be essential for optimal long-term behavioral outcomes in children.