Vanillin is widely used in many applications. Chemically vanillin (4-hydroxy-3methoxybenzaldehyde) is a benzene derivative with three different substituents. Nature, number and arrangement of substituents in the benzene ring define values of physical and chemical characteristics of the individual aromatic compounds and materials which are composed of them. Thermochemical properties are fundamental characteristics of chemical compounds they have a crucial significance in evaluation of thermal effects of chemical reactions with their participation. Therefore, determination of standard enthalpy of formation of vanillin is an importance task. Commercial sample (Sigma-Aldrich Co) of vanillin was purified by fractional sublimation at the pressure of 0,2 kPa in the temperature interval from 313 K to 318 K. The purity of the used sample, according to perfomed chromatographic analysis, was found to be 99,94 %. Density of crystalline powder vanillin was determined by pycnometric method at 298,15 K and was found to be 1,33 ± 0,01 g cm-3. Specific energy of combustion of vanillin was measured in the bomb isoperibolic calorimeter BIC 100 (JSC "BMC", Belarus). The calibration of calorimeter was performed using the certified standard sample of benzoic acid (trade mark K-1) with a molar proportion of the main component 99,995 ± 0,001 % and with the specific combustion energy 26434,4 ± 0,6 J g-1. The value of the energy equivalent calculated from 12 experiments amounted 10242,48 ± 1,02 J K-1. The uncertainty represents the standard deviation of the mean. Calorimetric experiments were organized in such a way, which allows to ensure identity of conditions of calibration and research experiments. Samples in the form of compressed in the air pellets were burnt in the platinum crucible. The corrected temperature rise in all experiments was approximately the same: 2,597 ± 0,015 K for benzoic acid, 2,457 ± 0,022 K for vanillin. In order to test the calorimeter and the value of its energy equivalent, a series of experiments of the burning of salicylic acid had been carried out. The obtained value of energy of combustion is in good agreement with the literature data. The value of standard molar enthalpy of formation of vanillin in the crystalline state at 298,15 K, obtained by using bomb calorimeter, and the value of standard molar enthalpy of formation of vanillin in a gaseous state at 298,15 K, obtained by using ab initio calculations, were found. The values of enthalpy of sublimation of vanillin at 298.15 К, calculated on the basis of the difference between these values, amounted to be 100 ± 3 kJ mol-1.