Last name Костелло (Costello 
, Costelloe , Костелло 
) , in all the world, is a common surname. The last name Костелло is habitual in Ireland, where it is a common surname, Cayman Islands, where it is quite a common surname, and Australia (explore the name in all countries). In absolute terms, it most frequently occurs in the United States, the United Kingdom, and Ireland.