The hamlet name is Anglo Saxon in origin, and means "island farm", referring to an island in the River Thame that flows by the hamlet. The medieval village of Eythrope is deserted and all that remains are some earthen banks and ditches on the eastern side of Eythrope Park. There was a manor house at this hamlet as early as 1309, when it was the home of the Arches family. It was extended in 1610 by Sir William Dormer.
William Stanhope (1702–1772) embellished Eythrope House around 1750. Stanhope employed Isaac Ware to build new stables (now lost) and follies in the garden and park. Two of these buildings survive: the grotto by the lake, and the bridge over the River Thame. The house was demolished in 1810-11 by Philip Stanhope, 5th Earl of Chesterfield.
In 1875, the manor at Eythrope was bought by Alice de Rothschild. She was the sister and companion of Baron Ferdinand de Rothschild who owned the neighboring estate Waddesdon Manor. The new house at Eythrope was not built on the site of the old manor. While building was in progress Alice fell ill with rheumatic fever and was advised to avoid damp conditions at night. As Eythrope was next to the river Thame, the plans were altered. The house was built without bedrooms as a place to house her collections and entertain guests during the day.
Alice chose one of the Rothschild family's favourite architects George Devey who had worked at nearby Ascott House, Aston Clinton House and Mentmore Towers. Eythrope was something of a deviation from his usual approach. It is constructed in red brick with stone dressings. With its twisting chimneys, turrets and gables, it is a mixture of Devey's usual Jacobean style and the French Renaissance architecture of Waddesdon Manor. This is especially noticeable on the concave roof to the round tower, and the gable on the garden facade which are particularly reminiscent of Waddesdon. Because of its small size the house was christened "The Pavilion" or the "Water Pavilion".
As in other Rothschild homes, French paneling and furniture dressed the rooms. Alice also collected Renaissance sculpture, paintings and maiolica ware.
Around the house, Alice developed 30 hectares of highly ornamental and innovative gardens that rivaled the splendor of Waddesdon Manor. She also created a large kitchen garden and added the Old English Tea House (now lost) to the historic parkland. A large, long stable block (listed grade II), built in stone and half-timber, with references to Waddesdon Manor, as well as three picturesque lodges, were probably designed by W Taylor & Son of Bierton. House parties from Waddesdon Manor would drive the four miles for tea, taking a steam launch up the river to the tea house.
In 1922 following Alice's death, The Pavilion was inherited by James Armand de Rothschild and his wife Dorothy. From 1922 to around 1939, they let it to the wife of Somerset Maugham who added bedrooms and bathrooms in a wing that later collapsed. In the 1950s the Rothschilds decided to give Waddesdon Manor, which they also had inherited, to the National Trust and move to the smaller pavilion. The house was improved and modernized. James de Rothschild died in 1957, before the house was ready. Following the transfer of Waddesdon, his widow Dorothy moved to Eythrope.