Ammonia (NH3) data were collected at regionally representative Canadian Air and Precipitation Monitoring Network (CAPMoN) sites. Radiello brand passive samplers were deployed at 2 or 5 m above the ground for two week periods and analyzed by the National Atmospheric Deposition Program (NADP) Ammonia Monitoring Network (AMoN). The passive samplers consist of a porous body containing a cartridge coated with phosphoric acid to which NH3 is sorbed. Cartridges were sonicated in deionized water to remove ammonium (NH4+) and then analysed by flow injection colorimetry to determine NH4+ in mg/L. Until December 2015, triplicate samples were deployed alongside a travel blank, which accompanies the samples in a sealed jar. From January 2016 – December 2017, deployments included single samples and a travel blank with 1-3 samples per year in triplicate. After this period, deployments included single samples with a travel blank, with three samples per year in duplicate. Ammonia data presented here in µg/m3 have been quality controlled and have replicates averaged, a variable sampling rate correction based on concurrent site temperature and pressure (after Massman, 1998) and a travel blank correction. Values before May 2015 were corrected using a site-specific travel blank average from May 2015 to December 2015. Values after May 2015 were corrected using a site-specific 6 month travel blank average. Original and uncorrected data can be obtained from AMoN.