In this study, amorphous cobalt hydroxide/polyaniline nanofibers (Co(OH)2/PANINF) composites were successfully prepared. The formation of amorphous Co(OH)2 with irregular surface structure was confirmed by x-ray diffraction, scanning electron microscopy, and selected-area electron diffraction. The non-enzymatic electrochemical sensor for the selective and sensitive determination of dopamine (DA) has been constructed by using Co(OH)2/PANINF composites modified glassy carbon electrode (Co(OH)2/PANINF/GCE), which exhibited excellent electrocatalytic activity toward DA, in a large part owing to the advantages of large surface area of amorphous Co(OH)2 and the synergetic effect between Co(OH)2 and PANINF. The electrochemical kinetics reveal that the DA oxidation involves two electrons and two protons in a quasi-reversible electrode reaction. Differential pulse voltammetry (DPV) studies show remarkable sensing performance for the determination of DA, with a low detection limit of 0.03 μM, and a wide linear range from 0.1 to 200 μM. From a broader perspective, the present study demonstrates that Co(OH)2/PANINF composites would be promising supporting materials for novel sensing platforms.