In the present work, for the first time, we report the fabrication of Cu2SnS3 (CTS)/CdS heterojunction for room temperature (27 °C) liquefied petroleum gas (LPG) sensing. The heterojunction is formed between sputter deposited CTS thin films and chemically bath deposited CdS thin films. The structural, morphological and optical properties of the thin films are evaluated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–visible spectroscopy techniques, respectively. The fabricated heterojunction quality is evaluated from the forward biased current-voltage (I-V) study and the influence of annealing treatment of p-CTS thin film on LPG sensing properties of the heterojunction has been investigated. The CTS/CdS heterojunction exhibits maximum LPG response of 56% at room temperature under exposure of 780 ppm LPG concentration with 31s and 56s response and recovery time, respectively. The device retained 95% gas sensing stability after time period of 60 days suggesting that the fabricated CTS/CdS heterojunction is reliable and promising for LPG sensing. The factors affecting LPG sensing performance and plausible gas sensing mechanism are discussed in this study.