Chemical preservatives are added to almost all foods to prevent spoilage and extend the shelf life, by inhibiting the growth and metabolic activity of microbes. Since most foods are subjected to heating, either by the consumer or by the manufacturer, the thermal behavior of a preservative is very important, in this study, the decomposition of calcium propionate was examined using simultaneous TG-DTA, with a rising temperature program and heating in dry nitrogen and air. The material initially decomposed to CaCO3, and then to CaO with further heating. The process was endothermic in nitrogen, but exothermic in air. Scanning electron microscopy (SEM) and powder diffraction was used to confirm the thermal analysis data.