The son of a Umatilla father and Shoshone mother, Washakie left the Umatilla while an adolescent to join his mother's tribe. By the 1840s he was chief of the Eastern Band (sometimes called Washakie's Band) of Wyoming Shoshone.

Although quite vain—he loved to be the centre of elaborate ceremonies—Washakie was kind and generous to whites passing through Shoshone territory under his control. He and his people assisted emigrants in crossing dangerous rivers and in recovering stray animals. Nine thousand grateful settlers once signed a document commending Washakie and his Shoshone Band for their exemplary treatment. Even when livestock belonging to whites destroyed his people's root and herding grounds, Washakie made sure no violent repercussions occurred.

In the fall of 1862, however, Washakie was unable to prevent a large number of his followers from joining the Bannocks in attacking and plundering white settlements. He took loyal members of his band with him to Fort Bridger in Wyoming and then reunited with the surviving Shoshone hostiles after the Bannocks were crushed at Bear River on January 29, 1863.

Washakie served as representative for both the Shoshone and the Bannocks at the 1868 Fort Bridger negotiations. As a result of these negotiations, Washakie's people surrendered the Green River Valley of eastern Utah and southern Wyoming to provide the right of way for the Union Pacific Railroad. During the Sioux War of 1876, Washakie sent many of his warriors to fight alongside U.S. government troops against the traditional enemies of the Shoshone. In fact, he himself frequently served as a scout during the U.S. Army's campaigns against the Cheyenne, Sioux, Arapaho, Ute, and other tribes hostile to the United States.

Washakie spent his last years on the Shoshone reservation, where he continued to rule as absolute dictator. When younger aspirants sought to depose him, the 70-year-old chief disappeared for two months. Then, just as the tribal council met to select a new leader, in strode Washakie with six scalps collected as proof of his undiminished prowess.