Tanner was born in Pittsburgh, Pennsylvania, the first of seven children.
His middle name commemorated the struggle at Osawatomie between pro- and anti-slavery partisans.
His father Benjamin Tucker Tanner (1835-1923) was a bishop in the African Methodist Episcopal Church, the first independent black denomination in the United States.
Being educated at Avery College and Western Theological Seminary in Pittsburgh, he developed a literary career.
In addition, he was a political activist.
His mother Sarah Tanner was born into slavery in Virginia but had escaped to the North via the Underground Railroad.

The family moved to Philadelphia when Tanner was young.
There his father became a friend of Frederick Douglass, sometimes supporting him, sometimes criticizing.
Tanner was born in Pittsburgh, Pennsylvania, the first of seven children. His middle name commemorated the struggle at Osawatomie between pro- and anti-slavery partisans. His father Benjamin Tucker Tanner (1835-1923) was a bishop in the African Methodist Episcopal Church, the first independent black denomination in the United States. Being educated at Avery College and Western Theological Seminary in Pittsburgh, he developed a literary career. In addition, he was a political activist. His mother Sarah Tanner was born into slavery in Virginia but had escaped to the North via the Underground Railroad. 
The family moved to Philadelphia when Tanner was young. There his father became a friend of Frederick Douglass, sometimes supporting him, sometimes criticizing.
Henry Ossawa Tanner