A new concept of polymer modification on cementitious materials was proposed. Cement mortars were modified using polyacrylate (PA) emulsion. Mixtures with polymer - cement ratios of 0, 5, and 10 wt.% were investigated in compressive strength and fracture properties at 0.5d, 0.75d, 1d, 3d, 7d and 28d. Compressive tests indicated a remarkable change of PA emulsion modified mortars from the early age to 28d. PA emulsion modification also gained considerable improvement in fracture properties. However, the test results revealed that the mechanical properties growth had not linear relationship with the PA emulsion addition. The mercury intrusion porosimetry (MIP) test proved that the optimization of PA emulsion addition should be emphasized in considering the pore introduction due to the emulsifier in PA emulsion. The principle of the PA emulsion modification was provided in a view of the microstructure of the mortars obtained from scanning electronic microscope (SEM) test and thermogravimetric (TG) analysis. © 2010 ASCE.