 Although he initially opposed founding Westminster Theological Seminary in 1929 when Princeton Theological Seminary was re-organized by the denomination along semi-modernist lines, he agreed to serve on Westminster's board.He opposed Machen's creation of an independent missions board, and, after Machen was censured for setting up this board, Macartney also opposed Machen's Presbyterian Constitutional Covenant Union.Ultimately Macartney resigned from Westminster's board rather than go along with these developments.