Liquefied petroleum gas (LPG) is widely used as a cooking fuel as it has higher energy content and produces lower emissions compared to other traditional fuels. Due to massive demand for LPG, aside from its limited reserve, performance improvement of the LPG cook-stoves is essential. In the present work, the thermal efficiency of a traditional cook stove has been studied both experimentally and numerically for LPG fuel. Based on the knowledge from the computational model concerning flow field and species transport parameters, the conventional cook-stove design has been modified for improving the efficiency. In the modified design of the stove, attachment of an annular metal plate insert and introduction of an extended spill-tray to close the gap around the burner are considered. The modifications result in favourable guidance of the flow of secondary air and hot product gases of combustion to ensure better heat transfer rate to the loading vessel. The thermal efficiency of the modified cook-stove is around 73.6%, which is about 4.7 percentage point improvement from that of an identical stove without the insert and extended spill-try.