From 1978 to 1989, he also served as Dean of Washington National Cathedral. Previously, he served as Bishop Coadjutor from 1976 to 1977 and Bishop Suffragan from 1971 to 1976. He was the first African-American Bishop of Washington.
He was the first African American to be admitted as a student to the Virginia Theological Seminary in 1951.
Bishop Walker first came to Washington as the Canon of Washington National Cathedral. He was once arrested at a protest rally against apartheid at the South African Embassy.
From 1975 until his death in 1989, Bishop Walker served as President of the Board of Directors of Africare. The organization now presents the Bishop John T. Walker Distinguished Humanitarian Service Award each year in his honor.
To honor the first African-American Bishop of the Episcopal Diocese of Washington and all of his contributions, The Bishop John T. Walker School opened in September 2008 as a tuition-free, pre-kindergarten through eighth grade school for boys in Southeast, Washington, District of Columbia
lieutenant has been founded by the Episcopal Diocese of Washington and each year a grade will be added until the school has reached its first graduating 8th grade class in 2017-2018. Also named after Walker is the Bishop John T. Walker Learning Center in Washington, District of Columbia, whose mission is "to support, encourage, and facilitate life-long learning to all peoples through instruction, dialogue, exploration, human interactions, and exchanges". Bishop Walker died suddenly on September 30, 1989 at the age of 64, of heart failure following triple bypass surgery.
He is buried in Washington National Cathedral.