This paper presents the results of experimental investigations of the basic thermal property – the specific heat capacity of selected heterogeneous materials – graphene oxide rubber composites. The value of specific heat capacity was measured with a PerkinElmer DSC 8000 differential scanning calorimeter using modulated temperature mode of operation. The heterogeneous material under investigation was the graphene oxide/rubber composite, which is used in the production of roller bearing seals. Two types of rubber have been used as the basic matrix of composites: the hydrogenated acrylonitrile butadiene rubber and the fluoroelastomer. Graphene oxide reduced with sodium hypophosphite was applied as a compo-site filler. The main goals of the work was to expand the database of thermophysical properties of materials and to inves-tigate the influence of material heterogeneity on the results of specific heat capacity measurements obtained with small-sized test samples.