Black Elk Speaks tells the story of Black Elk's early life, beginning with his first childhood memories and concluding in 1890, when he was twenty-seven years old. The text also contains detailed information about Oglala Sioux customs and traditions, as well as first-person accounts of important historical events as witnessed by other living Native Americans. Black Elk sees his tale as one that extends far beyond his own experiences:

It is the story of all life that is holy and is good to tell, and of us two-leggeds sharing in it with the four-leggeds and the wings of the air and all green things; for these are children of one mother and their father is one Spirit.