Background:Prenatal polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) exposures may influence children’s neurodevelopment.Objective:We examined the association of prenatal PBDE and PCB exposures with children’s reading skills at ages 5 and 8 years, Full-Scale Intelligence Quotient (FSIQ), and externalizing behavior problems at age 8 years.Methods:From 239 mother–child pairs recruited (2003–2006) in Cincinnati, Ohio, we measured maternal serum PBDE and PCB concentrations, assessed child’s reading skills using the Woodcock–Johnson Tests of Achievement III (WJ-III) at age 5 years and the Wide Range Achievement Test-4 (WRAT-4) at age 8 years, tested FSIQ using the Wechsler Intelligence Scale for Children-IV (WISC-IV), and externalizing behavior problems using the Behavioral Assessment System for Children-2 (BASC-2) at age 8 years. We used multiple linear regression to examine the association of prenatal PBDE and PCB concentrations and reading, FSIQ, and externalizing behavior problems after adjusting for covariates.Results:An increase of Sum4PBDEs (BDE-47, BDE-99, BDE-100, and BDE-153) by 10 times was not significantly associated with reading scores at age 5 years at the p = 0.05 level but was inversely associated with Reading Composite scores (β: –6.2, 95% CI: –11.7, –0.6) and FSIQ (β: –5.3, 95% CI: –10.6, –0.02) at age 8 years; it was positively associated with the score for externalizing behavior problems (β: 3.5, 95% CI: –0.1, 7.2) at age 8 years. Prenatal Sum4PCBs (PCB-118, -153, -138-158, and -180) was not significantly associated with a child’s reading skills, FSIQ, and externalizing behavior problems.Conclusion:Prenatal PBDE concentration was inversely associated with reading skills and FSIQ and positively associated with externalizing behavior problems at age 8 years. No significant associations were found in prenatal PCB concentration.Citation:Zhang H, Yolton K, Webster GM, Sjödin A, Calafat AM, Dietrich KN, Xu Y, Xie C, Braun JM, Lanphear BP, Chen A. 2017. Prenatal PBDE and PCB exposures and reading, cognition, and externalizing behavior in children. Environ Health Perspect 125:746–752; http://dx.doi.org/10.1289/EHP478