Sinéad McCoole was born in New York in 1968. She came to live in Ireland at the age of four with her Irish-born parents, Michael and Barbara McCoole (nee Folan) and her siblings Fiona and Ciaran. Sinéad spent her childhood in Limerick before moving to Dublin in 1987.

She is a graduate of University College Dublin with an Honours degree in History and History of Art (1990) and a Masters in Modern Irish History (1992). She is married to Eamon Howlin and they have two children Eve and Edward.