Kidney ischemia/reperfusion injury (IRI) is a common and serious problem in hospitalized patients. Immune cell trafficking and leukocyte-endothelial adhesion potentiate kidney IRI. An important immunomodulatory role of T lymphocytes has been elucidated in IRI. Regulatory T cells are a lymphocyte subset that has recently been demonstrated to perform a protective role both in early injury from IRI as well as in later repair. The immune system also participates in distant organ effects during kidney IRI. Studies focusing on immune aspects of kidney IRI have enabled the discovery of promising novel therapeutic and diagnostic approaches.