The technology for manufacturing a film membrane of the metamizole-selective electrode containing ion associate metamizole-octadecylammonium ODAH+MT− as an electrode active component (EAC) has been proposed. The main potentiometric characteristics of the metamizole-selective electrode have been determined. The expediency of the proposed design of the metamizole selective electrode for the determination of metamizole in dosage forms has been substantiated. The best composition of the membrane (wt.%) of the metamizole-selective electrode has corresponded to: ODAH+MT−—5.3; 2-nitrophenyloctylether—63.1; poly(vinyl chloride)—31.6. Electrode-active component in the membrane phase functions as an ion associate ODAH+MT−. Potentiometric characteristics of metamizole-selective electrode have been determined, which corresponded to: linear range 1 × 10−2–1 × 10−4 with limit of detection 4.58 × 10−5 M, electrode function slope −48.5 mV/dec., working interval pH 4.5–7.3, response time 60 s. The potentiometric coefficients of selectivity of the metamizole-selective electrode with respect to various ions have been determined. The possibility of determining metamizole in a medicinal product has been tested. The results of the analyses show good agreement between the two methods (relative error less than 7.0%) with coefficients of variation less than 5% for MT-SE and iodometric methods.