Thickness dependence of the magnetic behavior in BiFeO3 films was investigated. BiFeO3 films endure a phase transition from a distorted rhombohedral-type to a monoclinic-type, and its saturation magnetization increases with a decrease in film thicknesses. These results confirm that the improved saturation magnetization isn't due to artifact factors, but is attributed to the gradual decrease in grain sizes and the gradual increase in canting angle with decreasing the film thickness which are driven by the strain and phase transition. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.008112esl] All rights reserved.