Polymer nanocomposites with carbon nanoparticle filling are interesting for their various applications. They have been researched as pressure sensors [1] as well as volatile organic vapour sensors [2]. Nanocomposites are made from a polymer matrix and carbon nanoparticles. Nowadays many commercial carbon nanoparticles are available, like carbon black (CB), single wall carbon nanotubes (SWCNT), multiwall carbon nanotubes (MWCNT), thermally exfoliated graphite (TEG), graphene and many variations of these fundamental types. Most of them have been reported to show sensor activity, when mixed in a nanocomposite as a single filler or as a mixture of various fillers. In this work we propose an improved filler. The starting material is pre-exfoliated graphite – TEG. The process includes two stages – firstly TEG is oxidized and secondly the oxidized product – graphene oxide (GO) – is reduced to acquire reduced graphene oxide (RGO). Oxidation process was done using modified Hummer’s method [3] with potassium permanganate (KMnO4) and sodium nitrate (NaNO3) in sulphuric acid as the solvent and reduction was done using sodium borohydride (NaBH4) with cobalt ion (CoCl2·6H2O) assistance [4]. Thermally exfoliated graphite undergoes oxidation more fully than commonly used graphite flakes, because of the pre-exfoliation. The synthesized graphene oxide has higher electrical resistance, because of oxygen functional groups which disrupt graphene plane sp2 conjugation. After reducing graphene oxide the electrical conductivity increases significantly, because of the restored π-bonds. The oxidation of graphite with a subsequent reduction is believed to be the most promising way for large scale graphene-like materials production [4]. Polyisoprene RGO nanocomposite sensor effect for mechanical deformation as well as for volatile organic vapours is investigated.