Nanocrystalline La1-x Co (x) Mn1-y Ni (y) O-3 (x = 0.2 and 0.4; y = 0.1, 0.3, and 0.5) thick films sensors prepared by sol-gel method were studied for their H2S gas sensitivity. The structural and morphological properties have been carried out by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Average particle size estimated from XRD and TEM analyses was observed to be 30-35 nm. The gas response characteristics were found to depend on the dopants concentration and operating temperature. The maximum H2S gas response of pure LaMnO3 was found to be at 300 A degrees C. In order to improve the gas response, material doped with transition metals Co and Ni on A- and B-site, respectively. The La0.6Co0.4Mn0.5Ni0.5O3 shows high response towards H2S gas at an operating temperature 250 A degrees C. The Pd-doped La0.6Co0.4Mn0.5Ni0.5O3 sensor was found to be highly sensitive to H2S at an operating temperature 200 A degrees C. The gas response, selectivity, response time and recovery time were studied and discussed.