A sensitive electrochemical sensor for determination of hydroxylamine has been introduced. This sensorprofits by promazine hydrochloride (PHC) as homogenous mediator and multiwall carbon nanotubesto improve the surface of carbon paste electrode as working electrode. Cyclic voltammetry (CV), linearsweep voltammetry (LSV), chronoamperometry, and differential pulse voltammetry (DPV) are used tostudy of the suitability of promazine hydrochloride, at the surface of multiwall carbon nanotube pasteelectrode (MWCNTPE), as a homogenous mediator for the electrocatalytic oxidation of hydroxylaminein aqueous solutions. Hydroxylamine hardly oxidizes at about +1.1 V at the carbon paste electrode (CPE),whereas catalytically oxidizes in presence of PHC as mediator at the MWCNTPE. The electrocatalytic peakcurrent of hydroxylamine oxidation shows a linear dependence on hydroxylamine concentration in therange of 0.008–0.100 M, by DPV in optimized conditions at pH 9.0. In addition, using LSV and in sameconditions calibration plot was obtained at hydroxylamine concentration in the range of 0.17–10.0 mM.The detection limit (3) was obtained 1.4 nM and 4.2 mM for DPV and LSV, respectively. Also, sensitivityin the DPV measurement was 476 A/M. Kinetic parameters such as electron transfer coefficient, ˛ anddiffusion coefficient, D, are also determined. The proposed method was successfully applied as a highlysensitive, selective, simple, and precise method for hydroxylamine determination in the real samples