The drug Quinidine is an antiarrhythmic agent, which is also used in the treatment of malaria. Quinidine belongs a class of the narrow therapeutic index drugs and its dosage needs to be efficiently controlled. The official method for quinidine determination is based on high performance liquid chromatography with ultraviolet detection. Electrochemical methods have been widely reported for drugs determination in formulations pharmaceutical due to their advantages, such as low-cost, fast and simplicity for the application in the quality control of drugs. In this context, we present, for the first time, an electrochemical sensor for quinidine determination using a boron-doped diamond (BDD) electrode with square wave voltammetry (SQW) detection. Electrochemical measurements were performed on an Autolab PGSTAT 128N potentiostat/galvanostat. Electrochemical cell was composed of three electrodes: BDD with a doping level of 8000 ppm ((0.13 cm2), Ag/AgCl (saturated KCl) and platinum wire as working, reference and auxiliary electrodes, respectively. The BDD electrode was pretreated cathodically in 0.5 mol L−1 H2SO4, applying a current of +0.001 A for 120 s and then applying −0.03 A for 360 s. This treatment of the BDD electrode was performed before each analysis. The electrochemical behavior of quinidine was evaluated by cyclic voltammetry in different pHs and electrolytes. The best condition for quinidine electrochemical detection was obtained using a 0.25 mol L-1 sulfuric acid solution as electrolyte support, where quinidine showed two irreversible oxidation processes at +0.7 and +1.6 V (vs Ag/AgCl) on BDD. The generated product of quinidine oxidation at 1.62 V presented a reduction process at +0.3 V on DDB. The mass transport of quinidine was investigated and the oxidation process is controlled by diffusion at BDD. The second oxidation process of quinidine at BDD (1.6 V vs Ag/AgCl) is more sensitive for detection and quantification of this drug. However, the reduction process generated by second anodic peak of quinidine was selected to determine this drug due to its more selectivity for detection in pharmaceutical samples. Thereby, before the quinidine detection by SWV using BDD electrode, the application of an oxidation potential and its duration time were optimized at +1.7 V and 90 s, respectively. The parameters of the SWV technique were optimized with amplitude of 90 mV, step of 8 mV and frequency of 60 Hz. In these conditions, the repeatability for determination of 100 μmol L-1 quinidine was performed with a low relative standard deviation of 1.5% (N = 8). Two linear ranges were obtained to quantify quinidine, from 0.2 to 5.2 μmol L-1 and 10.3 to 55.0 μmol L-1, both with linear regression coefficients more than 0.99. The limit of detection (LOD) was calculated to be 0.03 μmol L-1 and the addition-recovery studies in pharmaceutical samples containing quinidine were around 100 %. Therefore, the proposed method has been shown to be promising for a simple, fast and selective analysis of quinidine drug. Furthermore, the use of an unmodified electrode as BDD can be an interesting alternative for the quality control of drugs with lower cost and waste generation than the official methods.