Polyethylene terephthalate (PET) currently occupies an important space in the manufacture of bottles for carbonated beverages and mineral water, however, its use has become another pollution problem in the world, due to the fact that most of them end up in landfills, increasing the volume of plastics waste. The present investigation focuses on the analysis of recycled polyethylene terephthalate (RPET) analyzing whether it is possible to modify the thermal behavior of this plastic, by adding flame retardant, with the aim of improving its thermal properties. The thermal properties of the mixture and the degradation were evaluated by thermogravimetric analysis (TGA) and Dynamic Thermal Analysis (DTA), characterizing its decomposition process in increase of temperature, showing the little variation of the behavior of the mixture of RPET and % of MCA as a flame retardant additive compared to virgin PET.