A simple route has been adopted for the fabrication of polyurea using polycondensation of 4,4'-diphenylmethane diisocyanate and 1,4-phenylene diamine. Amalgamation of polystyrene, polyurea and functional graphene (F–G) yielded a series of nanocomposite foams. The morphological, electrical, mechanical, thermal, and flammability properties of materials were investigated and found to be dependent upon the intrinsic properties of graphene-based materials and their state of dispersion in matrix. Field emission scanning electron microscopy revealed a strong interaction between polystyrene/polyurea and functional graphene surface forming unique layered cellular structure. Mechanical results revealed a synergistic interaction between F–G and polystyrene/polyurea matrix providing a shielding mechanism against graphene layer damage during compression. The 10% thermal decomposition temperature of polystyrene/polyurea/F–G 1–5 foams measured was in the range of 432–470℃. UL 94 showed V-1 rating for polystyrene/polyurea foam, while polystyrene/polyurea/F–G 1–5 foams attained V-0 rating. Water absorption capacity was improved steadily with the time and was maximum after 96 h for polystyrene/polyurea/F–G 5 foam (4.53%). Functional graphene also produced excellent electrical conductivity improvement in polystyrene/polyurea/F–G 5 foam (10¹) relative to polystyrene/polyurea/F–G 1 foam (10^–2) and neat polystyrene/polyurea foam materials (10^–7).