Mackintosh was born in Inverness, and attended a physical training college in Birmingham before becoming a teacher. Her literary career began when she was forced to give up regular work in order to care for her invalid father.
In five of the mystery novels she wrote under the name of Josephine Tey, the hero is Scotland Yard Inspector Alan Grant (he appears in a sixth, The Franchise Affair, as a minor character). The most famous of these is The Daughter of Time, in which Grant, laid up in hospital, has friends research reference books and contemporary documents so that he can puzzle out the mystery of whether King Richard III of England murdered his nephews, the Princes in the Tower. Grant comes to the firm conclusion that King Richard was totally innocent of the death of the Princes. (The novel has influenced later mystery writers, most notably Barbara Mertz, who writes under the name "Elizabeth Peters". Mertz refers explicitly to Tey in "The Murders of Richard the Third," which sets a country-house murder mystery among a group who believe that Richard III was innocent.)
The Franchise Affair also has a historical context: although set in the 1940s, it is based on the 18th-century case of Elizabeth Canning. The Daughter of Time was the last of her books published during her lifetime. A further crime novel, The Singing Sands, was found in her papers and published posthumously.
As Gordon Daviot she wrote about a dozen one-act plays and another dozen full-length plays, but only four of them were produced during her lifetime. Richard of Bordeaux was particularly successful, running for fourteen months and making a household name of its young leading man and director, John Gielgud.
Proceeds from Tey's estate, including royalties from her books, were assigned to the National Trust.
Tey appears as a main character in An Expert In Murder (Faber 2008) by Nicola Upson, a detective story woven around the original production of Richard of Bordeaux. The second novel in the series, Angel with Two Faces, was published in 2009; further novels are planned.
Tey is mentioned in the 1982 Stephen King novella, Apt Pupil.
The heroine of Mary Stewart The Ivy Tree uses Brat Farrar as a model when impersonating the missing heir to an estate. She describes the book as "the best of them all".