All allografts suffer a number of unavoidable ischemic insults. These, starting with brain death and ending with reperfusion, are very troublesome, as ischemia-reperfusion injury (IRI) is demonstrated to be a major cause of allograft damage in various types of transplantations. To counter the threat this poses to allograft function, investigators have worked diligently over the past decades in clinical settings and in the laboratory to understand the pathophysiology and immune mechanism underlying IRI hoping to ultimately devise strategies that lessen its detrimental effects on allografts. Herein, we review the major immune components of the IRI dynamic process. Better understanding of the cellular pathophysiological processes underlying IRI will hopefully result in the design of more targeted therapies to prevent the injury, hasten repair, and minimize chronic progressive allograft damage.