Lead-free tetragonal Ba(Cu1/3Nb2/3)O3 (BCN) was chosen to enhance the multiferroic characteristics of rhombohedral BiFeO3 (BFO). When the aerosol-deposited film with a composition of 0.9BFO–0.1BCN, chosen to be near that of the morphotropic phase boundary, was annealed at 600°C for 1 h, the film showed superior dielectric, ferroelectric, and magnetic properties to those of pure polycrystalline BFO films. TEM revealed that BCN addition and subsequent annealing process enlarged the lattice constant of the BFO film along the 〈111〉 direction. The greatly enhanced multiferroic properties were attributed to the distorted lattice structure induced by the BCN addition and the high residual stress effect.