Born in 1936 in Calcutta, Tully is the son of a wealthy English accountant. He spent the first decade of his childhood in India, albeit without the allowance of socializing with Indian people, before going to England for schooling. He was educated at Twyford School, Marlborough College and at Trinity Hall, Cambridge, where he studied Theology. After Cambridge, he considered becoming a priest in the Church of England but abandoned his vocation after just two terms at Lincoln Theological College admitting later that he had doubts about "trusting [his] sexuality to behave as a Christian priest".

Mark Tully joined the BBC in 1964 and moved to India in 1965 to work as the India Correspondent. He covered all major incidents in South Asia during his tenure, ranging from India-Pakistan conflicts, Bhopal gas tragedy, Operation Blue Star (and the subsequent assassination of Indira Gandhi, anti-Sikh riots), Assassination of Rajiv Gandhi to the Demolition of Babri Masjid.

Tully resigned from BBC in July 1994, after an argument with John Birt, the then Director General. He accused Birt of "running the corporation by fear" and "turning the BBC into a secretive monolith with poor ratings and a demoralised staff".

Tully was made an Officer of the Order of the British Empire in 1985 and was awarded the Padma Shree in 1992. He was knighted in the New Year Honours 2002 and in 2005 he received the Padma Bhushan.

Tully has written several books based on India including India in Slow Motion (co-author Gillian Wright), No Full Stops in India, The Heart of India, Divide & Quit, Last Children of the Raj, From Raj To Rajiv- 40 Years Of Indian Independence, India — 50 years of Independence, India's Unending Journey and Amritsar: Mrs. Gandhi's Last Battle. In the area of religion Sir Mark has authored The Lives of Jesus to accompany the BBC series and Four Faces: A Journey in Search of Jesus the Divine, the Jew, the Rebel, the Sage.

The anonymously authored Hindutva Sex and Adventure is a novel featuring a main character with strong similarities to Tully. Tully himself has stated that "I am amazed that Roli Books should publish such thinly disguised plagiarism, and allow the author to hide in a cavalier manner behind a nom-de-plume. The book is clearly modelled on my career, even down to the name of the main character. That character's journalism is abysmal, and his views on Hindutva and Hinduism do not in any way reflect mine. I would disagree with them profoundly".