The objective of the present work was to characterize rutin and quercetin by thermogravimetric (TG) and DSC coupled to a photovisual system. The kinetic parameters, rate constant (k), activation energy (E) and reaction order (n) were determined by isothermal and dynamic TG measurements. The results from the TG curves showed the decomposition of the two substances occurring in four stages. The DSC data reveal the presence of several phase transitions for the two compounds. The DSC-photovisual method confirmed the decomposition and polymorphic process for the quercetin and rutin, respectively, according to the literature.