Preparation of high-quality electrolyte films on porous substrates is critical to the fabrication of high-performance solid-state ionic devices such as solid oxide fuel cells and chemical sensors. In this study, a colloidal process has been investigated for the preparation of BaCeO3-based electrolyte films on both dense and porous substrates for electrochemical applications. The important processing variables affecting the microstructures of green films are identified and optimized to obtain uniform, crack-free green films of BaCe0.8Gd0.2O3 with high packing density of the electrolyte particles. Further, dense ceramic films of BaCe0.8Gd0.2O3-based electrolyte have been successfully fabricated on different substrates by careful process control. In addition, observations indicate that small amounts of additives can dramatically influence the densification behavior of barium cerate-based electrolyte films.