Shaffer was a Bevin Boy coal miner during World War II, and took a number of jobs including bookstore clerk, and assistant at the New York Public Library, before discovering his dramatic talents.

Encouraged by this success, Shaffer continued to write and established his reputation as a playwright in 1958, with the production of Five Finger Exercise,[4] which opened in London under the direction of John Gielgud and won the Evening Standard Drama Award.

Shaffer's next piece was a double bill, The Private Ear and The Public Eye, two plays each containing three characters and concerning aspects of love.

The Royal Hunt of the Sun (1964) presents the conquest and killing of the Inca ruler Atahuallpa by the conquistador Francisco Pizarro in Peru, while Black Comedy (1965) takes a humorous look at the antics of a group of characters feeling their way around a pitch-black room – although the stage is actually flooded with light.

A journey into the mind of a seventeen-year-old stableboy who had plunged a spike into the eyes of six horses, Equus ran for more than 1,000 performances on Broadway.

The latter production, which ran in New York City until February 2009, required the stableboy to appear naked; its star, Daniel Radcliffe, was still associated with the Harry Potter film series intended for general audiences, and this led to mild controversy.

This tells the story of Wolfgang Amadeus Mozart and court composer Antonio Salieri who, overcome with jealousy at hearing the "voice of God" coming from an "obscene child", sets out to destroy his rival.

[2] While on a trip to Ireland shortly after his 90th birthday, Shaffer died on 6 June 2016 at a hospice facility in Curraheen, County Cork.

In 1989 the Hamburg-based Alfred Toepfer Foundation awarded Shaffer its annual Shakespeare Prize in recognition of his life's work.