We describe a method to measure in vivo migration of human T cells by using the near-infrared (NIR) dye IRDye800CW. Labeling of Epstein-Barr virus-specific T cells with IRDye800CW did not affect viability, proliferation, or T cell function. Following tail vein injection into mice bearing subcutaneous tumors, the NIR signal could be measured in vivo at the tumor site. Analysis of tumors revealed T cell infiltration and an increased NIR signal, confirming T cell migration. To test specific migration with IRDye800CW, tumors were modified to express CCL5 to measure site-specific migration. The NIR signal was increased at CCL5-secreting tumors compared with control tumors. Together, these data suggest that IRDye800CW may be used to study the trafficking of T cells in a small animal model and may have potential as a short-term reporter molecule for human immunotherapy studies.