In this paper, the thermal stability and specific heat capacities of four imidazolium based ionic liquids namely 1-ethyl-3-methyl imidazolium octylsulfate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1,3-dimethyl-imidazolium dimethyl phosphate and 1-butyl-3-methylimidazolium chloride have been experimentally analysed using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The thermal stability was assessed by conventional and high resolution modulated TGA with the temperature range of 0 to 700 °C. The specific heat capacity was measured by using DSC within the temperature interval of 0 to 200 °C. The factors influencing the thermal stability and heat capacity of ionic liquids were studied. The thermal analysis results indicate that 1-ethyl-3-methylimidazolium octylsulfate exhibited excellent thermal stability even at 440 °C while 1-ethyl-3-methylimidazolium diethyl phosphate obtained a maximum specific heat capacity of 4.52 J/g.K. © 2020 Published under licence by IOP Publishing Ltd.