Since Tau have many races within their ranks, some of those just happen to be humans. Some humans within the Tau empire that have defected from the Imperium to join the Greater Good. These humans are known as the Gue'vesa, which literally means human helper in Tau and they fight in the Fire caste, even against other humans.

The T’au Empire hosts a growing population of allied and client races, most notably the Kroot, Vespid, Nicassar, Demiurg, and even some Human Gue’vesa. This is part of what makes the T’au unique and provides an interesting contrast with the xenophobia of the Imperium of Man.