Undoped and (1 mol%) Sm3+-doped LaAlO3 nanoparticles were synthesized by solution combustion technique utilizing sucrose as fuel. These rhombohedral perovskite nanoparticles thin films were prepared by spin coating on the ITO glass substrate. The XRD, SEM and TEM results show that the 40–60 nm crystallites are formed. The Photoluminescence Emission spectra and CIE coordinates show the enhancement of the yellowish orange color from Sm3+-doped LaAlO3 nanoparticles under the excitation wavelength of 406 nm. LPG detection was carried out for 0–1000 ppm concentrations. The sensor response of the Sm3+-doped LaAlO3 thin films was perceived to be > 87% for the detection of LPG through enhanced response as well as recovery time. Also, the stability analysis implied that the % sensor response remained favorably steady over a time period of 30 days. Owing to the improved % sensor response, quick response and recovery along with greater stability, these thin-film sensors showed better applications for detection of LPG leakage at room temperature.