FeTa and FeTaN thin films have been fabricated by sputter deposition from separate Fe and Ta magnetron sources. Microstructural investigations revealed that FeTa binary alloy films undergo a nanocrystalline to amorphous transition at about 17 at% Ta. This transition is associated with rapid simultaneous reductions in coercivity and saturation magnetization and increases in hardness and resistance to plastic deformation. Below 17 at% Ta the films exhibit a single-phase bcc structure and their lattice spacing increases linearly with Ta addition in agreement with Vegard's law, which indicates the incorporation of Ta in substitutional sites. The grain size and coercivity of the bcc binary films is seen to increase considerably with increasing Ta content. The addition of nitrogen causes a decrease in grain size, which is accompanied by a reduction in coercivity and an enhancement of hardness.