In this study, twenty-four amperometric dot microsensors based on carbon materials, (e.g., graphite (G) and graphene (GR) and carbon nanopowder (CN)), unmodified and modified with TiO2, and phthalocyanines: basic phtalocyanine (Pc), Fe(III)phthalocyanine ((FePc)-Pc-III) and Fe(II)phthalocyanine ((FePc)-Pc-II) are evaluated and tested for their ability for the analysis of serotonin (5-HT) in biological fluids (e.g. urine samples), using differential pulse voltammetry (DPV). Cyclic voltammetry (CV) was used to optimize the working conditions, e.g., pH, and electrolyte for the amperometric dot microsensors revealing (0.1 mol L-1) KCl and pH = 3.0 phosphate buffer as the optimum electrolyte and pH conditions for the assay of serotonin. The selected amperometric dot microsensors with preference to the G-(FePc)-Pc-III followed by the GR-(FePc)-Pc-III modified microsensors were used for the reliable analysis of serotonin in urine samples, with recoveries higher than 94.00%. (C) 2014 The Electrochemical Society. All rights reserved.