In this work, the thermal decomposition of benzoylformic acid was studied computationally, including the decarboxylation reaction by two different mechanisms and an additional one for the decarbonylation of the compound. The PBE functional and 6-311+G(d,p) basis set in the gas phase and the aqueous solution were used. Transition states were modeled, kinetic and thermodynamic parameters were calculated for each reaction, and bonds evolution were tracked along the reaction coordinate by analysis of Wiberg bond indices. Two-step decarboxylation mechanism, initially proposed for the decomposition of pyruvic acid was found to be a probable mechanism for benzoylformic acid in gas phase, compared to the one-step decarboxylation and decarbonylation reaction.