Sn4+-doped BiFeO3 (BFO) nanofibers have been fabricated by sol-gel based electrospinning method with nanofiber diameter in the range of 30-100 nm in the annealed state. The leakage current density dropped by two orders of magnitude in 3% Sn-doped BFO nanofibers compared to undoped BFO samples. Our density functional theory (DFT) simulation results indicate that Sn4+ prefers to occupy the Fe3+ site in BFO with a formation energy of 1.89 eV. The impurity Sn acts as shallow donor with a low transition energy level of 41 meV. Furthermore, an enhancement in the saturation magnetization was simultaneously observed for 3% Sn-doped nanofibers, which correlated well with our theoretical calculations. In other words, by carefully tailoring the degree of Sn doping in BFO nanofibers, we can reduce the leakage current and concurrently enhance the magnetic moment. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim