(In1-xMnx)(2)O-3 films were grown by radio frequency-magnetron sputtering technique. Effect of Mn doping on the structural, optical, and magnetic properties of films is investigated systematically. The detailed structure analyses suggest that Mn ions substitute for In3+ sites of the In2O3 lattice in the valence of +2 states, and Mn-related secondary phases or clusters as the source of ferromagnetism is safely ruled out. All films show typical room temperature ferromagnetism. The saturation magnetization M-s increases first, and then decreases, while carrier concentration n(c) decreases monotonically with Mn doping, implying that the ferromagnetism is not directly induced by the mediated carriers. The optical bandgap E-g of films decreases monotonically with the increase of Mn concentration, and there exists a linear functional dependence between E-g and n(c)(2/3), which is consistent with Burstein-Moss shift arguments. It can be concluded that the ferromagnetic order in Mn-doped In2O3 films is intrinsic, arising from Mn atoms substitution for the In sites of In2O3 lattice. The oxygen vacancies play a mediation role on the ferromagnetic couplings between the Mn ions. (C) 2013 American Vacuum Society.