Currently, perovskite structures have had an important impact in the development of gas sensors. In this work, perovskite LaCoO3 nanoparticles were synthesized by a simple, economic and reproducible processing by the solution method. The reactive precursors were nitrates of lanthanum and cobalt, using ethylenediamine as a chelating agent and distilled water as solvent. The gel formed by the solvent evaporation (through microwave radiation) was dried at 200 °C and later calcined at 300, 400, 500, 600, and 700 °C for 5 h. The samples were analyzed by X-ray diffraction, infrared spectroscopy, thermogravimetry, scanning, transmission, and atomic force microscopies, and nitrogen physisorption. These analyses confirmed the formation of LaCoO3 nanoparticles (size ~ 47 nm) at relatively low temperatures. The particles showed a continuous connectivity, generating a porous surface with a fibrous appearance. Starting with the synthesized powders, pellets were made and tested as gas sensors in carbon monoxide and propane atmospheres (at concentrations of 0–300 ppm) at different temperatures (25, 150, 250, and 350 °C). The nanoparticles presented high sensitivity, with a greater response in the propane atmosphere.