Silicone softeners are widely used in the textile industry to improve the soft handling and aesthetic feel of textiles. These compounds can influence the thermal characteristics and flammability of polyester fabrics, which need to be addressed as important issues of human safety. To do this, the thermal degradation and flammability of macroemulsion and microemulsion silicone coated polyester fibers were studied with various analytical techniques, namely, differential scanning calorimetry, thermogravimetric analysis, dynamical mechanical thermal analysis, and limited oxygen index testing. It has been stated that the electrostatic and hydrophobic interactions of silicone emulsions with polyester can affect their thermal stability. On the other hand, the silicone emulsions present on the surface of poly(ethylene terephthalate) provide a three-dimensional scaffold, which produces faster combustion than pyrolysis. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012