This structure is the western of the pair, and the fact that two such monuments were built in deliberate proximity raises questions that have occupied archaeologists for generations: were they constructed at the same time, by the same community, for related or even complementary purposes?

Court tombs are among Ireland's oldest surviving monuments, typically dating to around 4000 BCE or earlier. The form involves a roofless, roughly semicircular forecourt of upright stones opening into one or more covered gallery chambers, the whole originally buried beneath a long cairn of earth and rubble. They were places of communal burial and probably ritual, used over extended periods rather than for single interments. The dual court tomb at Carrowkilleen was documented by Ruaidhrí de Valera and Seán Ó Nualláin in their Survey of the Megalithic Tombs of Ireland, Volume II, covering County Mayo, published by the Stationery Office in Dublin in 1964. That survey remains a foundational reference for megalithic studies in the west of Ireland, and Carrowkilleen features as one of the more unusual examples in a county that contains a remarkable concentration of prehistoric monuments.