A foamed polymer nanocomposite system is developed as an ablative for thermal protection applications. Polymer nanocomposite foams exhibit better thermal properties with the inherent benefit of being lightweight. In this study, Polyetherimide (PEI) was compounded with nanoclay to enhance the flame retardant property. A thermoplastic elastomer, Kraton, was added to improve the mechanical strain. Samples with various compositions of nanoclay and Kraton were foamed using a batch solid-state foaming process. The thermal protection performance of the material system was characterized with an oxy-acetylene flame ablation test. It is shown that foaming helped reduce the mass loss of the samples during the ablation test. The loadings of nanoclay and Kraton and the foam density can be used to optimize the thermal protection performance. The foams obtained in this study had a graded structure with an overall porosity of 20–60%.