In most graphene-based electrochemical applications, graphene nanoplatelets (GNPs) have been applied. Now, for the first time, electrochemical properties of GNPs, namely, its electrochemical activity, potential window, and double-layer capacitance, have been investigated. These properties are compared with those of carbon nanotubes (CNTs). GNP- and CNT-coated electrodes were then applied for electrochemical oxidation of endocrine-disrupting chemicals. The GNP-coated electrode was characterized by atomic force microscopy and electrochemical techniques. Compared with the CNT-coated electrode, higher peak current for the oxidation of 4-nonylphenol is achieved on the GNP-coated electrode, together with lower capacitive current. Electrochemical oxidation of 2,4-dichlorophenol, bisphenol A, and octylphenol in the absence or presence of 4-nonylphenol was studied on the GNP-coated electrode. The results suggest that GNPs have better electrochemical performance than CNTs and are thus more promising for electrochemical applications, for example, electrochemical detection and removal of endocrine-disrupting chemicals.