McClintock is the eldest son of Henry McClintock, formerly of the 3rd Dragoon Guards, by his wife Elizabeth Melesina, daughter of the Ven. George Fleury, D.D., archdeacon of Waterford. His uncle is John McClintock (1770–1855) of Drumcar House.
In 1835 McClintock becomes a member of the Royal Navy as a gentleman volunteer, and joins a series of searches for Sir John Franklin between 1848 and 1859. He masters traveling by using human hauled sleds, which remain the status quo in Royal Navy Arctic and Antarctic overland travel until the death of Captain Robert Falcon Scott RN in his bid to reach the South Pole. In 1848-49, McClintock accompanies James Clark Ross on his survey of Somerset Island. As part of Capt. Henry Kellett‘s expedition 1852 to 1854, McClintock travels 1,400 miles by sled and discovers 800 miles of previously unknown coastline.
In 1854 the explorer John Rae travels west from Repulse Bay, Nunavut and learns from the Inuit that a ship has been abandoned somewhere to the west. Previous expeditions have not searched the area because they believe it to be ice-blocked. In April 1857 McClintock agrees to take command of the Fox, which belongs to Lady Franklin, and searches for her husband in the area west of Repulse Bay. At Disko Bay he hires thirty sled dogs and an Inuit driver. It is a bad year for ice and from September he is frozen in for eight months. The following year, 1858, is another bad year and he does not reach Beechey Island until August. He enters Peel Sound, finds it blocked by ice, backs up, enters Prince Regent Inlet in the hope of passing Bellot Strait. He is glad to extricate himself from this narrow passage and finds winter quarters near its entrance.
In February 1859, when sledging becomes practical, he goes south to the North Magnetic Pole which had been found by James Clark Ross in 1831. Here he meets some Inuit who tell him that a ship has been crushed by ice off King William Island, the crew has landed safely and that some white people have starved to death on an island. In April he goes south again and on the east coast of King William Island meets other Inuit who sell him artifacts from Franklin’s expedition. William Hobson, who has separated from him, finds the only written record left by Franklin on the northwest corner of the island. They also find a skeleton with European clothes and a ships boat on runners containing two corpses. They get as far south as Montreal Island and the mouth of the Back River.
McClintock returns to England in September 1859 and is knighted. The officers and men of the Fox share a £5,000 parliamentary reward. The tale is published in The Voyage of the ‘Fox’ in the Arctic Seas: A Narrative of the Discovery of the Fate of Sir John Franklin and His Companions. London, 1859.
In 1872–1877 McClintock is Admiral-Superintendent of Portsmouth Dockyard. In 1879 he is appointed Commander-in-Chief, North America and West Indies Station with the flagship HMS Northampton. McClintock leaves the Royal Navy in 1884 as a Rear Admiral. He dies on November 17, 1907. He is buried in Kensington Cemetery, Hanwell, Middlesex.
On October 29, 2009 a special service of thanksgiving is held in the chapel at the Old Royal Naval College in Greenwich, to accompany the rededication of the national monument to Sir John Franklin there. It also marks the 150th anniversary of Sir Francis Leopold McClintock’s voyage aboard the yacht Fox.
Admiral Sir Frances Leopold McClintock has several portraits in the National Portrait Gallery, London.