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 (k(o)) of 5.6 x 10(-3) cm s(-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 0.25 V and PAR at 0.50 V vs. Ag/AgC1 (3.0 mol L-1 KCl). The analytical curves obtained were linear in the range from 3.2 x 10(-6) to 3.2 x 10(-5) mol L-1 and from 2.8 x 10(-6) to 1.9 x 10(-5) mol L-1 for DA and PAR, respectively, with detection limits of 2.0 x 10(-7) for DA and 5.3 x 10(-8) mol L-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.