Measurements of the far-infrared transmission of the canted-spin antiferromagnet NiF2 using the technique of Fourier-transform spectroscopy are described. Resonant absorptions were found at ν1=3.33+/-0.05 cm-1 and ν2=31.14+/-0.1 cm-1 with applied field H=0 and temperature T~0. Using the resonance relations derived by Joenk and Bozorth from Moriya's model, these give anisotropy and exchange parameters E=1.66 cm-1 and 8 JD=482.2 cm-2. A good fit is obtained to the measured magnetic-field dependence of both modes for g⊥=2.35 which, along with the measured perpendicular susceptibility, gives 8J=125 cm-1 and D=3.86 cm-1. The temperature dependence of ν2 was measured between 1.2 and 65°K (TN=73.2°K) and is found to be in agreement with the Zener theory when the temperature dependence of the sublattice magnetization is estimated from neutron-diffraction intensity measurements. The linewidth and strength of mode 2 were also measured as a function of T, and are discussed qualitatively.