The effects of steam and autoclave curing on the mechanical properties and microstructure of alkali activated slag mortars (AAS) were investigated within the scope of this study. Slag was activated by the mixtures of sodium hydroxide and sodium silicate, in different Na₂O and M_s (SiO₂/Na₂O) ratios. Test results showed that high strength mortars can be produced with very low alkali content under autoclave curing as a result of better pore size distribution, higher rate of hydrated parts of slag grains which leads to a better microstructure formation. A compressive strength value of 70MPa has been reached by incorporation of 2% Na₂O under autoclave curing. Nevertheless, steam curing presents similar mechanical performance with autoclave curing for AAS mortar activated by the solutions with high M_s values. Both curing methods were significantly effective in terms of reducing drying shrinkage of AAS mortars.