Abstract Wildfires are the largest terrestrial source of atmospheric ammonia (NH3), yet their impacts on NH3 concentrations and ammonium (NH4+) deposition remain poorly quantified. In this study, we evaluate the effects of the record‐breaking 2023 Canadian wildfire season on NH3 concentration and NH4+ deposition across the Upper Midwest. This study integrates satellite observations, ground‐based data, and in situ aircraft measurements. In May–June 2023, NH3 concentrations increased at 83% of ground sites, and NH4+ deposition flux rose at 100% of ground sites in the Upper Midwest. Satellite data showed significantly higher column‐averaged NH3 in 47% of grid cells in the Upper Midwest. On 1 August, a smoke plume over the Midwest corresponded with an AEROMMA flight observing enhanced NH3, NH4+, carbon monoxide, and acetonitrile. These findings highlight the substantial impact of wildfire smoke on NH3 and NH4+ at regional scales, with implications for nitrogen cycling, air quality, and atmospheric modeling.