Max Nicholson, as he was known to all, was born in Kilternan, Ireland to English parents. His family moved to England in 1910, settling in Staines. He became interested in birdwatching, beginning his list of birds in 1913.
He was educated at Sedbergh School in Cumbria and then Hertford College, Oxford from 1926, winning scholarships to both. At Oxford he read history, and visited Greenland and British Guiana as a founder member of the University's Exploration Club.
He already had published his first work in 1926, Birds in England, and had three similar books published soon after. In The Art of Bird-Watching (1931), he discussed the potential of co-operative birdwatching to inform the conservation debate. This led, in 1932, to the foundation of the British Trust for Ornithology, of which he was the first treasurer and later chairman (1947 - 1949).
He joined the civil service in 1940, during World War II working for the Ministry of Shipping, then the Ministry of War Transport, attending conferences at Quebec and Cairo, and was with Winston Churchill at the post-war peace conferences at Yalta and Potsdam. From 1945 until 1952 he was private secretary to Herbert Stanley Morrison. He also chaired the committee for 1951's Festival of Britain.
In 1947-1948, with the then director general of the United Nations' scientific and education organisation UNESCO, Julian Huxley, he was involved in forming the International Union for the Protection of Nature (IUPN) (now International Union for Conservation of Nature (IUCN)).
In 1949 he oversaw Part 3 of The National Parks and Access to the Countryside Act which established a British state research council for natural sciences and 'biological service', The Nature Conservancy (1949-1973), and allowed for the legal protection of National Nature Reserves and Sites of Special Scientific Interest (SSSI). He replaced Captain Cyril Diver as Director General of The Nature Conservancy in 1952 and served until 1966, just after the Conservancy lost its independent status. During his leadership the Conservancy established itself as a research and management body which promoted ecology as having broad relevance and application to land use decision-making and management.
In 1952, while in Baluchistan, he contracted polio, which left him with a limp. In 1961, he was part of the organising group that created the World Wildlife Fund (WWF) (now the World Wide Fund for Nature) and he was also a founder of the International Institute for Environment and Development. In 1966 he set up and headed Land Use Consultants, remaining with them until 1989. In 1978 he was instrumental in founding the ENDS Report which was later to become a highly influential journal for environmental policy specialists.
He was also chief editor of The Birds of the Western Palearctic ("BWP", 1977-1994, OUP) from 1965-1992. He was President of the Royal Society for the Protection of Birds from 1980-1985, helped set up the New Renaissance Group and was a trustee of Earthwatch Europe.
He once appeared as a guest on Desert Island Discs.