Harcourt died in his sleep at his London townhouse at 69, Brook Street (now the Savile Club) in the early hours of 24 February 1922, aged 59. He had taken an overdose of a sleeping draught, and there were rumours of suicide following accusations of sexual impropriety by Edward James, a young Etonian who later became an important collector of surrealist and other contemporary art. James's mother spread the story in society although the accusations remained unknown by the wider public for fifty years. An inquest was held as to the cause of death, which returned a verdict of death by misadventure; the underlying cause being given as heart failure and sudden oedema of the lungs brought on by a dose of Bromidia, which he had been prescribed as a sleep aid. According to the coroner, who found extensive heart disease, the amount of Bromidia he had taken would not have caused death in a healthy person. According to his valet, there was only a very small amount of Bromidia left in the bottle the prior evening, which Harcourt did not take regularly.