In his private life, Hartley spent much of his time rowing, swimming, and socializing, often traveling with friends.

His writing career began with short story collections, with his first novel, The Shrimp and the Anemone, published at age 49.

He was known for writing about social codes, moral responsibility and family relationships, and many of his works portray passion as leading to disaster.

[9][10] In 1910, Hartley finally settled at Harrow School, where he was a Leaf Scholar and earned prizes in reading and English literature.

[14] In 1916, with the arrival of conscription, Hartley joined the army, and in February 1917, he was commissioned as an officer in the Norfolk Regiment;[15] however, he never saw active duty because of a weak heart.

While there, Hartley made a number of literary friends, including Lord David Cecil and Aldous Huxley.

He also met the writer and socialite Elizabeth Bibesco, whose support and status catapulted Hartley into aristocratic British circles.

[19] In 1924, he met Constant Huntington of G. P. Putnam, who published his first volume of short stories, Night Fears, in that year, as well as his novella Simonetta Perkins in 1925.

The Saturday Review called the young writer "one of the most hopeful talents", and The Calendar of Modern Letters said that Simonetta Perkins was a "distinguished first novel".

Modern critics have called it his most dangerous novel, as Hartley explored infatuation and sexuality in a way considered less respectable at the time.

Critics reviewed the books favourably, often marvelling at the author's ability to create characters that were lovable despite their high-class status.

Walter Allen in the New Statesman called the trilogy "one of the few masterpieces in contemporary fiction", and other critics agreed in similar reviews.

Hartley had intended The Go-Between to be a commentary on the loss of innocence and morality; however, he was shocked when he found that many readers sympathized with the characters he thought should be hated.

He also entertained many guests – including the painter Henry Lamb, the art critic Adrian Stokes, and the novelist Leo Myers – and often set his writing aside to focus on social events.

[28] During the later part of his life, Hartley resided in London at Rutland Gate, enjoying rowing on the Avon River in his free time.

Hartley became relatively reclusive during these years, no longer attending the social gatherings that had punctuated much of his earlier life.

[26] Hartley enjoyed reading a number of his contemporary authors, such as Elizabeth Bowen, Edith Wharton, and Henry Green.

The first novel in which he included homosexual characters was My Fellow Devils – but instead of painting their sexuality in a favourable light, he portrays it as the reason for a friendship's ruin.

[35] Cynthia Asquith was a support through much of Hartley's career, publishing some of his early writings in her anthologies and welcoming him into her social circles.

[36] The major influences on Hartley's work were Nathaniel Hawthorne, Henry James, and Emily Brontë.

[42] In columns Hartley wrote for The Daily Telegraph, he often expressed a distaste for the flaws of contemporary culture.

[29] In 1971, the director Joseph Losey made a film based on Hartley's novel The Go-Between, starring Julie Christie and Alan Bates.

[39] In 1991, the filmmaker Clive Dunn directed a documentary about Hartley for Anglia Television, titled Bare Heaven.