Introduction: Despite a growing body of research, our understanding of the impact of air pollution exposures on cognition remains poor. To address this knowledge gap we estimated the association between exposure to ambient air pollution and cognitive outcomes among older adults who were part of the National Social Life, Health, and Aging Project (NSHAP). Methods: We linked participant data to fine particle (PM2.5), ozone (O3), and nitrogen dioxide (NO2) exposures. Cognitive function was assessed in 2010-2011 using the Chicago Cognitive Function Measure (CCFM) that measures 8 cognitive domains on a 20 point scale. PM2.5 exposures were estimated using spatio-temporal models, while O3 (April-September only) and NO2 concentrations were obtained from the nearest EPA monitors. Associations between cognitive function and air pollution levels were examined with linear regression models controlling for race, gender, education, age, season, smoking, geographic region, and median household income of census tract. Results: IQR increases in 1 to 7 year moving average PM2.5 exposures were significantly associated with decreased CCFM scores, with a -0.22 (95% CI -0.44, -0.01) point change in CCFM score for a 1 year moving average. Likewise, 1 to 7 year moving averages of NO2 exposures were associated with similar decreases (-0.13 (95% CI -0.34, 0.08) and -0.27 (95% CI -0.48, -0.07), respectively). In contrast, exposures to O3 associated with small but significant increases in scores (0.17, 95% CI 0.02, 0.31 for 2 yr moving average exposure). Conclusions: We found that increases in PM2.5 and NO2 exposures are significantly associated with changes in cognitive test scores. Our study is unique in its use of spatio-temporal models for estimating PM2.5 exposures, and use of the CCFM, a reliable measure of cognitive function. These results suggest that limiting exposure to PM2.5 and NO2 may prevent deterioration in cognitive function that affects an increasing number of older adults.