Syntactic foams are finding new applications where their thermal stability and high temperature response are important. Therefore, the high temperature response of these advanced composites needs to be characterized and correlated with various material parameters. The present study is aimed at evaluating the effect of microballoon (hollow particle) volume fraction (I broken vertical bar) and wall thickness (w) on thermoanalytical characteristics of epoxy matrix syntactic foams containing glass microballoons. These composites are characterized to determine the glass transition temperature (T (g)), the weight loss, and the char yield. It is observed that T (g) decreases and the char yield increases due to the presence of microballoons in the resin. The T (g) is increased with an increase in I broken vertical bar but is not significantly affected by w. The thermal stability is increased by increasing w and is relatively less sensitive to I broken vertical bar. Understanding the relations between thermal properties of syntactic foams, the microballoon wall thickness, and microballoon volume fraction will help in developing syntactic foams optimized for mechanical as well as thermal characteristics. Due to the increased interest in functionally graded syntactic foams containing a gradient in microballoon volume fraction or wall thickness, the results of the present study are helpful in better tailoring these materials for given applications.