Additive manufacturing (AM) technologies: electron beam melting, selective laser melting, and laser engineered net shaping have been used to manufacture Ti-6Al-4V. However, to adopt AM processed titanium alloys, various processing parameters and post-process treatments have been used to obtain improved mechanical properties to meet standard requirements. In this study, fatigue performance, failure mechanism, and fatigue crack growth behavior of Ti-6Al-4V made via different AM technologies were systematically compared and discussed. The pros and cons of AM technologies in making fatigue resistant titanium alloys were critically discussed, as well. The role of microstructure, surface roughness, and porosity on fatigue crack initiation and crack growth was quantitatively analyzed to clarify the effect of post-process treatments such as surface milling, HIPing and shot peening on fatigue property and behavior of additively manufactured titanium alloys.