The invention provides a non-efflorescing cementitious mortar composition, free of reactive silica material, in the form of a dry-mortar composition or an aqueous mortar composition, comprising a) ordinary portland cement, b) calcium aluminate cement, c) calcium sulfate, and d) an aqueous polymer dispersion or a water-redispersible polymer powder of polymers based on one or more monomers from the group consisting of vinyl esters, (meth)acrylates, vinyl aromatics, olefins, 1,3-dienes and vinyl halides and, if required, further monomers copolymerizable therewith.