Despite the importance of understanding the connection between air pollution exposure and diabetes, studies investigating links between air pollution and glucose metabolism in nondiabetic adults are limited. We aimed to estimate the association of medium-term air pollution exposures with blood glucose and glycated hemoglobin A1c (HbA1c) among nondiabetics. This study included observations from nondiabetic participants (n =7,108) of the population-based Heinz Nixdorf Recall study at baseline (2000–2003) and follow-up examination (2006–2008). Daily fine particulate matter (aerodynamic diameter≤2.5 μm, PM ; aerodynamic diameter≤10 μm, PM ), accumulation mode particle number (PN ), and nitrogen dioxide (NO ) exposures were estimated at participants’ residences using the spatiotemporal European Air Pollution Dispersion (EURAD) chemistry transport model. We evaluated the associations between medium-term air pollution exposures (28- and 91-d means) and glucose metabolism measures using mixed linear regression and adjusting for season, meteorology, and personal characteristics. A range of other exposure windows (1-, 2-, 3-, 7-, 14-, 45-, 60-, 75-, 105-, 120-, and 182-d means) were also evaluated to identify potentially relevant biological windows. We observed positive associations between PM and PN exposures and blood glucose levels e.g., 28-d PM : 0.91 mg/dL (95% CI: 0.38, 1.44) per 5.7 μg/m . PM , PM , and PN exposures were positively associated with HbA1c e.g., 91-d PM : 0.07 p.p. (95% CI: 0.04, 0.10) per 4.0 μg/m . Mean exposures during longer exposure windows (75- to 105-d) were most strongly associated with HbA1c, whereas 7- to 45-d exposures were most strongly associated with blood glucose. NO exposure was not associated with blood glucose or with HbA1c. Medium-term PM and PN exposures were positively associated with glucose measures in nondiabetic adults. These findings indicate that reducing ambient air pollution levels may decrease the risk of diabetes. https://doi.org/10.1289/EHP2561.