In the present study, microcrystalline cellulose (MCC) reinforced cementitious composites have been developed using a short and less energy intensive physical dispersion technique. MCC–cement mortar specimens were prepared through addition of aqueous MCC suspensions to the cement-sand mixture. Aqueous MCC suspensions (0.4%, 0.8%, 1.2%, 1.6% and 2% MCC, by weight) were prepared through magnetic stirring of pre-soaked MCC powder for only 45 min. The flow behaviour of freshly prepared MCC-mortar paste as well as bulk density, mechanical performance, microstructure, porosity, water uptake and hydration products of developed cementitious composites were characterized. It was noted that with the increase of MCC content, the flow of mortar paste decreased significantly. Maximum improvements of 20.5% in flexural strength, 19.8% in compressive strength, 100% in flexural modulus and 27.2% in fracture energy were achieved after 28 days of hydration. Mechanical performance was found to be better at lower MCC concentrations and at early hydration days. The addition of MCC significantly reduced the pore size of cementitious matrix, leading to increased dry bulk density and reduced water uptake as compared to the plain mortar specimens.