John Pitcairn Mackintosh was born on 24 August 1929, in Simla, India. He was educated at Melville College in Edinburgh and the studied at Edinburgh University where he attended the lectures of, among others, Dr. Balfour-Melville. He also studied at Balliol College, Oxford, and at Princeton.

Mackintosh went on to become an Assistant Lecturer at Glasgow University, 1953-54, Lecturer in History, Edinburgh University, 1954-61, Senior Lecturer in Government at the University of Ibadan, Nigeria, 1961-63, and he was Senior Lecturer in Politics at Glasgow University, 1963-65, and Professor of Politics at the University of Strathclyde, 1965-66. Later in his life, 1977, he became part-time Professor and Head of the Department of Politics at the University of Edinburgh.

He had a political career too, contesting Edinburgh Pentlands for the Labour Party in 1959, and Berwick and East Lothian in 1964. He became MP for Berwick and East Lothian in 1966 succeeding William Anstruther-Gray, but in the February 1974 election he was defeated by the Conservative Michael Ancram. He regained it again in the second 1974 election, in October. Mackintosh was fierce proponent of devolution in Scotland.

His publications include The British cabinet (1962), Nigerian goverment and politics (1966), The devolution of power (1968), and The government and politics of Britain (1970). In addition he edited British prime-ministers in the twentieth century, Vol.1: Balfour to Chamberlain (1970) and British prime-ministers in the twentieth century, Vol.2: Churchill to Callaghan (1978). Mackintosh was also a freelance writer and television commentator.

John Pitcairn Mackintosh MP (Labour) died in office on 30 July 1978. He was succeeded in his constituency by John Home Robertson.