Hydrochlorothiazide/triamterene, also known as co-triamterzide, is a combination medication of hydrochlorothiazide and triamterene. It is used to treat high blood pressure and swelling. Specifically it is used in those who develop low blood potassium when on only hydrochlorothiazide. Due to side effect, their measuring is very important. This report introduces a new sensor based on glassy carbon electrode (GCE) modified with a multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (rGO) hybrid nanocomposite for electrochemical determination of triamterene (TRM) and hydrochlorothiazide (HCT) simultaneously. Impedance spectroscopy and scanning electron microscopy (SEM) were used for electrode modification process. The differential pulse stripping voltammetric (DPSV) responses of HCT and TRM were in linear with their concentrations, ranging from 0.5 to120 μM and 1.5 to 120μM respectively with correlation coefficients >0.99. The synergistic influence of MWNTs and graphene contributes to the excellent performance for the sensor, in simultaneous determination of HCT and TRM in pharmaceutical combinations. Display omitted