Thermogravimetric analysis (TG) provides information regarding mass changes in the sample resulting from heat treatment under controlled environment. However, it does not provide any chemical information regarding the gases evolved during the thermal degradation. Using FT-IR spectrometry in combination with TG, it is often possible to identify the evolved gases, and also monitor their evolution profiles during thermal degradation. In this study, we present the TG/FT-IR combined analysis of incineration and pyrolysis of some common plastics such as high density polyethylene (HDPE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS). This study demonstrates the utility of such combined analysis in providing useful information regarding the use of thermal treatment for recycling or incineration.