Sol-gel-derived LaCoO3 thin films were deposited on yttria-stabilized zirconia (YSZ) substrates from a lanthanum isopropoxide-cobalt acetate (with 2-methoxyethanol) precursor solution. A chelating agent (2-ethylacetoacetate) and polyethylene glycol (PEG) were used to modify the above-mentioned precursor solution. The La-Co precursor solution was sufficiently viscous, and transparent LaCoO3 gel films were prepared successfully using a spin-coating technique. Crystallization behavior and microstructure evolution were investigated using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). A single-phase perovskite thin film with the grain size of similar to 50 nm was obtained by heat-treating the spin-coated gel film at a temperature of 600 degreesC. SEM observations revealed that the microstructure of LaCoO3 thin films that were prepared from the precursor solution with PEG was porous, and the LaCoO3 thin film maintained its porous microstructure to a temperature of 800 degreesC.