Hooker was the son of a merchant's clerk and descendant of Richard Hooker, noted theologian of the 16th century. A fortuitous discovery in 1805 of a rare moss, which he communicated to James Edward Smith, founder of the prestigious Linnean Society (London), redirected his interests from general natural history to botany. His early education at Norwich Grammar School was followed by a voyage to Iceland in 1809, a period of extensive study in England, and a trip to France, Switzerland, and Italy in 1814–15, where he met some of the leading continental botanists. He married Maria Turner, daughter of the botanist Dawson Turner, in 1815. Joseph Dalton Hooker, the second of their five children, also became a famous botanist. In 1820 Hooker accepted the chair of regius professor of Botany at Glasgow, a position he held until 1841. Until his death at Kew, he was actively engaged in promoting the importance of botany. He was made a knight of Hanover in 1836.

Beginning with his Journal of a Tour in Iceland in the Summer of 1809, published in 1811, he had more than 20 major works as well as numerous periodical articles published in the following 50 years. His main interest was in cryptogamic botany (e.g., ferns, mosses, fungi), as shown by his publications British Jungermanniae, 1816; Musci Exotici, 1818–20; Icones Filicum, with R.K. Greville (1829–31); Genera Filicum (1838); and Species Filicum (1846–64). He also published important floristic studies—Flora Scotica (1821); The British Flora (1830); Flora Borealis Americana: or the Botany of the Northern Parts of British America (1840)—and was a pioneer in the study of economic botany. These publications—together with his own herbarium, which he generously made available to all scholars, and the journals that he founded and edited—made him the centre of English botany. The climax of his career came in 1841, when he was appointed the first director of Kew Gardens. Under his leadership, Kew Gardens became the world's leading botanical institution. Now a vast complex, including laboratories, a museum, a library, and greenhouses, it is a national showpiece as well as his personal monument. Before his retirement in 1865, he founded the Museum of Economic Botany at Kew (1847).