Principles of adipose graft survival at the recipient site have informed clinicians’ meticulous preparation and injection techniques of fat grafts with the overall goal of optimizing clinical results. In particular, the theory that grafts incur central necrosis due to limitations in nutrient and oxygen diffusion has been particularly influential for guiding structural fat grafting injection techniques. Broadly, fat graft injection technique depends on the intended clinical application, required harvesting and processing methods, and adipose parcel size. Supplemental techniques, such as platelet-rich plasma and microneedling, have also been incorporated into fat grafting approaches to maximize treatment potency. In this chapter, we describe the surgical principles governing diverse approaches to fat grafting, the underlying basis for injection techniques across clinical indications, and the current research that informs maximizing graft retention and adipose regenerative capabilities. At the highest level, the appropriate injection approaches are governed by clinical indication, which can be loosely categorized as structural, regenerative, and orthopedic. As fat grafting is used across many surgical specialties, the approaches described herein are thus cross-disciplinary and utilize state-of-the-art approaches to achieve the highest levels of patient care.