In the context of rapid urbanization and climate change in China, it is especially important to understand the effects of air quality on the subjective well-being of working adults because of their prolonged exposure to air pollutants. This study examines the relationship between ambient air pollutant emission levels and the subjective well-being of working adults using multilevel regression models based on a multilevel matching dataset formulated from the 2016 China Labor-Force Dynamics Survey, the 2016 China City Statistical Yearbook, and the 3rd-Quarter 2016 air pollution index released by the China National Environmental Monitoring Centre. In particular, we examine whether these air pollutants affect subjective well-being and compare the results by age, population density, and regional settings in China. The results show that increased CO emissions compromise the happiness of working adults (β = −0.1574, p < 0.05 for happiness; β = −0.1759, p < 0.01 for life satisfaction). This negative effect is substantially ameliorated among older working adults (β = 0.0002), but is significantly stronger in medium-density (β = −0.2521 for happiness; β = −0.2451 for life satisfaction) and high-density cities (β = −0.3997 for happiness; β = −0.5736 for life satisfaction). In addition, CO emissions have less effect on life satisfaction for adult workers living in western China (β = −0.1051). The findings of this study have a strong potential to help policymakers improve the quality of life of residents through better-targeted approaches.