The objective of this study was to find out the influence of curing age on microstructure in barium titanate - Portland cement composites. Barium titanate, BaTiO3 (BT) particles was mixed with Portland Cement (PC) and BT content of 50% by volume to produce the composites. All composites were cured in chamber of 60°C and 98% relative humidity for 1, 2, 3, and 7 days. Thereafter, scanning electron microscope (SEM) was used to examine the interfacial zone between cement and BT ceramics. SEM observation indicated that the BT-PC composite cured for 7 days clearly showed calcium silicate hydrate gel (an essential hydration product of Portland cement) surrounding the BT particles and has lower porosity. In BT-PC composite cured for 1 day, the gel can be seen but of less quantity and has higher porosity which clearly affected the interfacial zone. © (2011) Trans Tech Publications, Switzerland.