Well-crystallized spinel ZnFe2O4 thin films with good adhesion have been successfully prepared on glass substrates heated above 350 degreesC by a spray pyrolysis deposition from mixed zinc and iron nitrates aqueous solutions. The solution pH has an influence on the surface morphology of ZnFe2O4 films. A smooth and dense surface was obtained from the mixed solution with a pH of 2.0, while a rough and inhomogeneous surface could be observed from the solution with a pH of 8.0. The crystallite size of ZnFe2O4 films was found to be small, ranging from 10 to 21 nm as calculated from X-ray diffraction patterns, which is of interest for magnetic material applications. The indirect and direct band gap energies of the sprayed films were estimated to be 1.78 and 2.70 eV, respectively. A schematic illustration is proposed to show the possible deposition processes of ZnFe2O4 thin films by spray pyrolysis.