After Oxford, Mabey worked as a lecturer in Social Studies in Further Education at Dacorum College, Hemel Hempstead, then as a senior editor at Penguin Books.
He appeared in a 1975 episode of the BBC Television series The World About Us, "In Deepest Britain", with John Gooders and other naturalists, giving an unscripted narration of the wildlife observed during a country walk.
The book of the series Postcards from the Country: living memories of the British countryside (by Peter Marren and Mike Birkhead) includes a foreword by Mabey.
Between 2000 and 2002 Mabey suffered from depression, and his book Nature Cure, describing his experiences and recovery in the context of man's relationship with landscape and nature, was short-listed for three major literary awards: the Whitbread Biography of the Year, the Royal Society of Literature's Ondaatje Prize for evoking the spirit of place and the J. R. Ackerley Prize for Autobiography.
[9] Mabey has been awarded two Leverhulme Fellowships, and honorary doctorates by St Andrews, Essex and East Anglia for his contributions to nature writing.
[12] Mabey sat for sculptor Jon Edgar in Norfolk during 2007, as part of the Environment Triptych (2008)[13] along with Mary Midgley and James Lovelock.