The main objective of this study was to evaluate the relationship between mother's socioeconomic disadvantage and blood concentrations of inflammation-related proteins among extremely preterm newborns (<28 weeks gestation), a group at heightened risk of cognitive impairment when exposed to systemic inflammation. We measured the concentrations of 27 inflammatory and neurotrophic proteins in blood specimens collected a week apart during the first postnatal month from 857 extremely preterm newborns in the United States. We classified children according to 3 indicators/correlates of socioeconomic disadvantage, mother's eligibility for government-provided medical care insurance (Medicaid), mother's formal education level, and mother's IQ approximated with the Kaufman Brief Intelligence Test- 2. The risks of a top-quartile concentration of each protein on each of 5 days a week apart, on two occasions during the first two postnatal weeks, and during the next two weeks were modeled as functions of each indicator of socioeconomic disadvantage. The risks of top quartile concentrations of multiple (2-5) inflammation-related proteins on multiple days during the first two weeks were increased for each of the 3 indicators of socioeconomic disadvantage, while the risks of top quartile concentrations of selected neurotrophic proteins were reduced. Adjustment for socioeconomic disadvantage did not alter the relationships between protein concentrations and both low IQ and low working memory 10 years later. Among extremely preterm newborns, indicators of socioeconomic disadvantage are associated with modestly increased risk of systemic inflammation in postnatal blood during the first postnatal month and with a slightly reduced risk of a neurotrophic signal, but do not confound relationships between protein concentrations and outcomes.