This work investigates the influence of various alkaline activators (Na and K) on the properties of a Lebanese metakaolin-based geopolymer mortar. The first part of this work consisted to find and treat a local Lebanese source of kaolin. The metakaolin was later produced by the calcination of the local kaolin at a temperature reaching 700˚C. Once prepared the silica, alumina and alkali activator (either Na or K based) were mixed together in order to obtain the required mortars. Results indicated that the sodium based geopolymer mortars exhibit a greater compressive mechanical strength than the potassium based mortars.