The effects of processing conditions on the morphologies of Mn-doped BiFeO3 thin films have been investigated. BiFeO3 thin films were prepared on a SrTiO3 (001) substrate by CSD method. BiFeO3 grew epitaxially on SrTiO3 and Bi 2Fe4O9 has also orientation relationships with BiFeO3. It was found that the formation of Bi2Fe 4O9 was promoted in an O2 atmosphere. Island morphologies were observed in the BiFeO3 thin films after post-annealing at 1023K both in N2 and O2 atmospheres. The formation of the islands is promoted in an O2 atmosphere.