A sensor based on glassy carbon electrode (GCE) modified within reduced graphene oxide (RGO) and carbon black (CB) in a chitosan film (CTS) is presented. The combination of the nanomaterials with CTS provided a stable dispersion and could be successfully used as electroactive layer. By using the Nicholson method and the results obtained by cyclic voltammetry with the proposed RGO-CB-CTS/GCE, the heterogeneous electron transfer rate constant (k0) of 5.6×10−3cms−1 was obtained. The proposed electrode was applied for the simultaneous determination of dopamine (DA) and paracetamol (PAR). Employing square-wave voltammetry, DA presented an anodic peak at 0.25V and PAR at 0.50V vs. Ag/AgCl (3.0molL−1 KCl). The analytical curves obtained were linear in the range from 3.2×10−6 to 3.2×10−5molL−1 and from 2.8×10−6 to 1.9×10−5molL−1 for DA and PAR, respectively, with detection limits of 2.0×10−7 for DA and 5.3×10−8molL−1 for PAR. The developed sensor presented advantages such as simple preparation, low cost of the nanomaterials employed and a fast response. Besides, it could successfully apply in the determination of DA and PAR in biological samples. Display omitted •A thin film using reduced graphene oxide and carbon black in a chitosan film is proposed.•The proposed electrode is easy to prepare, presents low cost and fast response.•It was applied the simultaneous determination of dopamine and paracetamol.