Ahmadshah started his career as a customs officer at the Royal Customs and Excise Department, Kota Kinabalu on 1 March 1968. He was appointed Executive Officer (Rural) and was moved to Beaufort District Office as Assistant District Officer (Rural) on 10 November 1969. He was seconded to the National Paddy and Rice Board as Chief Officer from April 1979 until July 1983. He also worked as Secretary of State Public Service Commission (1983), Dakwah Officer of Sabah Islamic Affairs Council (October 1986 to January 1988), Secretary of the Islamic Council of Sabah (January 1988 to June 1994), Secretary of Internal Affairs and Research Office (1994 to 1995) and Director of the State Public Service Department (December 1995 to March 1998). He served as Deputy State Secretary (Administration) from 21 March 1998 to 8 December 2002. On 1 January 2003, he was sworn in as the ninth
Yang di-Pertua Negeri of Sabah. He served two full terms and stepped down on 31 December 2010. == Personal life and death ==