Air pollution has been linked to hypertension in the general population, but data on gestational hypertension (GH) are limited. We investigated air pollutants and toxics during preconception and early gestation in relation to GH risk in the Consortium on Safe Labor/Air Quality and Reproductive Health Study (2002-2008). Modified Community Multiscale Air Quality models estimated air pollution exposures among 6,074 singleton pregnancies with GH and 199,980 normotensives. Generalized estimating equations estimated relative risks per interquartile-range increment for pollutants and high exposure (≥75th percentile) for toxics, after adjustment for major risk factors. For an interquartile-range increment, GH risk was significantly increased by 18% for sulfur dioxide during the three months preconception; and 17% for nitrogen oxides, 10% for particulate matter <2.5 μm, 7% for particulate matter <10 μm, and 22% for sulfur dioxide during gestational weeks 1-20. High exposures to several polycyclic aromatic hydrocarbons both during preconception and the first trimester were significantly associated with 8%-20% higher GH risk. Further, preconceptional exposures to several volatile organic compounds were significantly associated with 11%-19% higher risk. Our findings suggest early exposures to criteria air pollutants, particularly from transport emissions, and high exposure to several air toxics during preconception may increase GH risk.