Directed energy deposition enables efficient fabrication of complex Ti-6Al-4V components, yet process-induced microstructural gradients and porosity across the build height remain poorly understood with respect to their effects on mechanical and fatigue performance. In this study, we investigate the relationships between directed energy deposition process parameters, the resulting microstructure, and anisotropic mechanical behavior. The study expands the current understanding of directed energy deposition-processed Ti-6Al-4V by providing a detailed analysis of microstructural evolution in both build directions and presenting new insights into fatigue properties. The microstructural and mechanical characteristics of the alloy are systematically described with an emphasis on their mutual relationship. The material exhibited a predominantly α’ martensitic microstructure, with no significant variation in phase fraction as a function of distance from the build platform, consistent with the measured hardness. Electron backscatter diffraction analysis did not reveal a pronounced crystallographic texture, whereas transmission electron microscopy observations identified deformation twins within the α’ phase. Porosity was mainly oriented perpendicular to the build direction. The combination of a martensitic microstructure and the presence of pores resulted in low ductility. Under cyclic loading, pores acted as crack initiation sites, while their planar orientation limited their effect on crack propagation, indicating that the mechanical response was governed primarily by the martensitic microstructure rather than pore-assisted crack growth. Overall, the results highlight the critical role of microstructure and inherent defects in controlling the mechanical behavior of additively manufactured components and provide a basis for process optimization and post-processing strategies such as heat treatment or hot isostatic pressing.