Grimond was educated at Eton College and Balliol College, Oxford, became a barrister, and in 1938 married Laura Bonham-Carter, a granddaughter of Herbert Asquith. After service in World War II, he entered parliament in 1950 as Liberal member for Orkney and Shetland, continuing to represent the constituency until he retired from politics in 1983. He was a life-long champion of Scottish devolution within the UK, and though often weary of the EEC's bureaucracy, was an early advocate of the EEC.
Grimond led the party through a difficult period in the late 1950s and early 1960s. The party he inherited commanded barely 2.5% of the vote. A man of considerable personal charm, charisma, and intelligence he was widely respected and inspired trust, and by the end of his tenure the Liberal party was once more a mainstream party. It was during his leadership that the first post-war Liberal revival took place- under Grimond the Liberals doubled their seats and won historic by-elections in Torrington (1958), Orpington (1962), and Roxburgh, Selkirk and Peebles (1965). In 1967, he made way for a younger, more dynamic leader, Jeremy Thorpe. In 1976, when Thorpe was forced to resign because of a scandal, Grimond stepped in as caretaker leader until the election of a replacement, David Steel.
Among other posts, Grimond was a barrister and publisher in the 1930s, an army Major during World War II,Secretary of the National Trust for Scotland from 1947 to 1949, and held the Chancellorships of the University of Edinburgh and the University of Kent. His many books include "The Liberal Future" (1959- credited with reinvigorating radical liberalism as a coherent modern ideology), "The Liberal Challenge" (1963), and "Memoirs" (1979). On leaving parliament, he was created a life peer ("Baron Grimond of Orkney"). He remained devoted to his former parliamentary constituency, and was buried in the Orkneys.