Following surface mining, peat is typically used as an organic amendment to cap reconstructed soils in the Athabasca oil sands region of Alberta. Yet, very little is known about its ability to provide available nitrogen (N) in these soils. Hence, the overall objective of this study was to measure soil nitrogen (N) availability throughout the year in five peat amendments. Specific objectives were: (1) to examine seasonal variability in soil labile N pool sizes (nitrate, ammonium, dissolved organic N, and microbial biomass N), and (2) to determine in situ net nitrification, ammonification, and mineralization rates using the resin-core technique. Results from this field incubation method indicated a strong seasonal variability in net mineralization rates, with maximum positive values in the fall, and low or negative rates in winter. Net ammonification rates, which were significantly correlated to soil moisture content, were significantly smaller and showed smaller seasonal fluctuations and fewer differences among peat materials than net nitrification rates. Furthermore, the contribution of net nitrification to total net mineralization rates was characteristically higher than what is typically observed in undisturbed boreal forest soils. Taken together, results indicate that net nitrification processes may control nitrogen availability in these reclaimed soils.