A simply sensitive sensor based on a reduced graphene oxide–TiO2 nanocomposite modified glassy carbon electrode (RGO–TiO2/GCE) was developed for the electrochemical determination of an antimalarial drug, hydroxychloroquine (HCQ). The modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Electrochemical test showed that the RGO–TiO2 electrode had stronger electrochemical activity and higher effective real surface area than that of TiO2 electrode and bare electrode. The electrochemical response of RGO–TiO2 nanocomposite modified electrode toward HCQ oxidation was studied by CV, chronoamperometry (CHA), chronocoulometry (CHC) and square-wave voltammetry (SWV). Interestingly, RGO–TiO2/GCE indicated an excellent electrocatalytic activity for HCQ. Under the optimal experimental conditions, a linear relationship between the peak current and the concentration was obtained, ranging from 0.25 to 500 μM, with the detection limit (S/N = 3) of 12.5 nM and quantification limit (S/N = 10) of 0.97 μM. Furthermore, the proposed sensor was successfully applied to the determination of HCQ in pharmaceutical (tablets) samples. In summary, the developed sensor was low cost and efficient, making it potentially attractive for practical sample analysis application of HCQ.