This work presents the analytical method development for iron and copper determination in ethanol fuel. This method was developed using stripping voltammetry with a glassy carbon electrode modified with Nafion/Carbon‐nanotubes. With linear sweep stripping voltammetry was achieved a limit of detection of 7.1×10−7 mol L−1 for Fe3+ and 5.1×10−8 mol L−1 for Cu2+. The amperometric sensitivities were 2.0×106 µA mol−1 L for Fe3+ and 2.8×107 µA mol−1 L for Cu2+. The recovery study showed that the method has good accuracy and repeatability, with recovery of 108 and 103 % for Fe3+ and Cu2+ respectively.