Background Both elemental metals and particulate air pollution have been reported to influence adult blood pressure (BP). The aim of this study is to examine which elemental components of particle mass with diameter ≤2.5 μm (PM) are responsible for previously reported associations between PM and neonatal BP. Methods and Results We studied 1131 mother-infant pairs in Project Viva, a Boston-area prebirth cohort. We measured systolic BP (SBP) and diastolic BP (DBP) at a mean age of 30 hours. We calculated average exposures during the 2 to 7 days before birth for the PM components-aluminum, arsenic, bromine, sulfur, copper, iron, zinc, nickel, vanadium, titanium, magnesium, potassium, silicon, sodium, chlorine, calcium, and lead-measured at the Harvard supersite. Adjusting for covariates and PM, we applied regression models to examine associations between PM components and median SBP and DBP, and used variable selection methods to select which components were more strongly associated with each BP outcome. We found consistent results with higher nickel associated with significantly higher SBP and DBP, and higher zinc associated with lower SBP and DBP. For an interquartile range increase in the log Z score (1.4) of nickel, we found a 1.78 mm Hg (95% CI, 0.72-2.84) increase in SBP and a 1.30 (95% CI, 0.54-2.06) increase in DBP. Increased zinc (interquartile range log Z score 1.2) was associated with decreased SBP (-1.29 mm Hg; 95% CI, -2.09 to -0.50) and DBP (-0.85 mm Hg; 95% CI: -1.42 to -0.29). Conclusions Our findings suggest that prenatal exposures to particulate matter components, and particularly nickel, may increase newborn BP.