We have prepared single-crystal nickel ferrite films, several microns thick, on cleaved MgO surfaces both by chemical transport and by reactive sputtering. The structures were characterized by x-ray diffraction and by measurements of the static magnetic moment. The resonance field strengths parallel and perpendicular to the (100) plane of the films, and the linewidths were measured. Though the static film properties were in accordance with the corresponding values of bulk material, the resonance quantities varied over a wide range. In comparison with the theoretical values for ideal nickel ferrite films according to the Kittel resonance equation, the measured resonance fields for a smooth film may be explained by an additional quasi-isotropic internal field; a rough or granulated film, also obtained by chemical transport, is best described by a strong internal field (≥1300 Oe) which is anisotropic with regard to parallel and perpendicular film directions. The films prepared by reactive sputtering show some peculiarities. The linewidths of all films are relatively large (700–1700 Oe). We suggest two-magnon scattering for the line broadening, and for the line shape, superimposed magnetostatic and spin-wave modes excited by demagnetization fields.