Pull-out mechanisms for different common steel fibers were investigatedusing adapted pull-out tests performed in-situ in an x-ray micro tomograph(µXRT). High-resolution volume images from the µXRT scans enable clearvisualization of aggregates, pores, the fiber and the fiber-matrix interface.Furthermore, the natural density speckle pattern from aggregate distributionand pores was found suitable for Digital Volume Correlation (DVC) analysis.From the DVC results it was possible to visualize and quantify the straindistribution in the matrix around the fiber at the different load levels up tofinal failure, being marked by either pull-out or fiber rupture. This studydemonstrates that strain measurements within the concrete matrix can beobtained successfully using µXRT imaging and DVC analysis, which leads to anincreased understanding of the interaction mechanisms in fibre reinforcedconcrete under mechanical loading.