Hadden replaced Matt Williams and was appointed on 15 September 2005. Hadden coached the Merchiston Castle School 1st XV after being appointed Head of Physical Education at the school in 1983. He coached several Scottish age-group teams before being appointed assistant coach of the Caledonian Reds in 1997. He was later appointed coach of Edinburgh Gunners (now Edinburgh Rugby) in 2000 prior to becoming the Scotland coach. He has since coached Scotland to notable wins over England and France in the 2006 Six Nations and again winning the Calcutta Cup against England in the 2008 Six Nations. He parted company with the national side on 2 April 2009 after a second consecutive disappointing Six Nations where they finished second bottom after winning just one match.