AbstractMicrocracks inevitably occur over time in cement composites, and they pose a threat to the safety and durability of concrete structures, especially when environmental conditions are considered. Microstructural analysis can be an effective alternative for the estimation of compressive strength, which is often difficult to monitor and follow and requires destructive analysis techniques. For this study, macrostructure and microstructure analyses were conducted of cementitious composites prepared with the nanofillers with the highest performance in the literature. In cementitious composites, 2.41 times more calcite content was obtained with the use of 0.05% graphene nanopellets, and 2.59 times more portlandite content was obtained with the use of 0.1% carboxylated-multiwall carbon nanotubes. It was concluded that the linear regression model was effective for the estimation of the compressive strength of nanofiller-blended cementitious composites, demonstrated by an R2 value of 0.984. Based on the macrostructure and microstructure analyses results, the optimum nanofiller was determined by the technique for order preference by similarity to ideal solution (TOPSIS) method to be carboxylated–multiwall carbon nanotubes with a usage rate of 0.1%.