The aim of this work is to predict the micromechanical properties of interfacial transition zone (ITZ) by combining experimental and numerical approaches. In the experimental part, hardened cement paste (HCP) cantilevers (200 μm × 100 μm × 100 μm) attached to a quartzite aggregate were fabricated and tested using micro-dicing saw and nanoindenter, respectively. In the modelling, comparable digital specimens were produced by the X-ray computed tomography (XCT) and tested by a discrete lattice model. The fracture model was calibrated by the experimental load-displacement curves and can reproduce the experimental observations well. In the end, the calibrated model was used to predict the mechanical behaviour of ITZ under uniaxial tension, which can be further used as input for the multi-scale analysis of concrete.