The microstructure of two CrN thin films and their interface with an MgO substrate were investigated with Transmission Electron Microscopy (TEM) and Electron Energy-Loss Spectroscopy (EELS). Sample A, a Cr/CrN bi-layer, had a single crystalline structure. Sample B, a CrN single layer with a thickness of more than 1 µm, formed a polycrystalline columnar configuration. High-Resolution TEM (HRTEM) studies revealed that both layers were grown epitaxially on the substrate and the generation of misfit dislocations at the interface has been observed. In both layers edge type dislocations in end-on orientation were found at the CrN/MgO interface and characterized. For a detailed investigation of the strain fields across the interface and around the dislocations cores the Geometric Phase Analysis was applied. Displacement and two-dimensional relative strain maps were calculated. In addition EELS measurements were realized for the CrN single layer. A spatial distribution of the two components (CrN film and MgO substrate) was performed with Multiple Linear Least Squares fitting technique (MLLS fitting).