Nitrite type hydrocalumite is a material which can adsorb the chloride ions causing the corrosion of reinforcing bars and liberate the nitrite ions ($NO_2{^-}$) inhibiting the corrosion, and provides excellent corrosion-inhibiting property to the reinforcing bars in reinforced concrete by the addition of it to concrete. On the other hand, various redispersible polymer powders have been commercialized to manufacture the construction materials in the form of prepackaged-type products, which have rapidly been developed for lack of skilled workmen in construction sites. In recent years, terpolymer powders of improved quality have been developed and commercialized as cement modifiers. However, the properties of polymer-modified mortars using the terpolymer powders have not been studied till now. The purpose of the present paper is to examine the strengths and corrosion inhibition of polymer-modified mortars using a VA/E/MMA terpolymer powder with nitrite-type hydrocalumite (calumite) to develop the prepackaged-type materials for dry mortar. Polymer-modified mortars using a newly developed terpolymer powder as polymeric admixtures with the calumite are prepared with various calumite contents and polymer-binder ratios, and tested for strengths and corrosion inhibition. On the whole, the strength properties of VA/E/MMA terpolymer powder-modified mortars are considerably improved with an increase in the polymer-binder ratio regardless of the calumite content. and are remarkably improved over unmodified mortar. It is concluded from the test results that the replacement of the portland cement with the calumite causes a marked improvement in the corrosion-inhibiting property of the polymer-modified mortars.