The appointment of Scott as editor follows the recent departure of the editors of the Daily Mirror and the Sunday Mirror, Richard Wallace and Tina Weaver.
All three titles are owned by Trinity Mirror.
Scott replaces Lloyd Embley, who as part of the editorial restructure is now the editor of the Daily Mirror and the Sunday Mirror.
Scott joined Trinity Mirror in 1999 and has been deputy editor of the Sunday Mirror for eight years.
He began his career at South West News Service in Bristol before moving to The Sun.
He has previously held the roles of news editor and then deputy editor at the Sunday Mirror.