In the last few years, several researches have been focused on the development of new materials capable to insulate and protect aerospace vehicles from the hyperthermal environment. Great attention was paid to the ablative Thermal Protection System (TPS) and particularly to the polymer nanocomposites, which is able to dissipate a relevant heat flux through various endothermic processes. Poly(phenylene oxide)/polyamide (PPO/PA) based nanocomposites have been already thermally analyzed in literature for this specific application. In this work the same materials were studied with the aim to understand their rheological and mechanical behavior. Nanocomposites at different loadings of commercial organomontmorillonite (Cloisite 15A) were produced by melt compounding with twin screw extruder, using a commercial blend of PPO/PA (Noryl GTX 914) as matrix. The melt viscosity of the materials were measured at low shear rates using a rotational rheometer, meanwhile, a capillary rheometer and higher shear rates were used to investigate the processability. At low shear rates, the viscosity was evaluated in dynamic state and transient shear flow tests were performed to study the response during start-up of single shearing experiment. The data collected from capillary rheometer were used to construct the Bagley diagrams and evaluate the pressure effects on the material viscosity. The mechanical tests were conducted on single filament materials obtained from capillary rheometer and data at different shear rates and capillary lengths were collected. A comparison between raw material and nanocomposites at different percentages of filler was made in order to understand the influence of the processing parameters on the properties of the final materials.