Daniel J. "Dan" Sullivan was born in 1875 to Hanora and Daniel A. Sulivan in Boston, MA. He was a classically trained pianist, and his father, a professional fiddle and flute player, introduced him to the Irish music scene in Boston. Dan Sullivan worked for the Steinway Piano Corporation in Boston before himself becoming a full-time professional musician. His focus shifted more exclusively toward Irish traditional music beginning around 1906, when he began writing music with Chauncy Olcott. He formed and led the dance-hall, gramophone, and radio band Dan Sullivan's Shamrock Band beginning in the 1920s, specializing in playing Irish traditional music and popular songs. He also recorded some of his own playing and compositions, both on piano rolls and on recording discs. In 1923, Sullivan opened his own piano store, which he operated until his death in 1948.