Ahmadshah began his education at Government Primary School Darau, Menggatal in 1952 and ended his secondary school session on 1967 at Louisiana Salle Secondary School, Tanjung Aru, Kota Kinabalu. He received a Diploma in Development Administration from South Devon College in the United Kingdom and Bachelor of Science (Political Science) from Indiana State University in the United States.
He started his career as Custom Officer at Royal Custom and Excise Department, Kota Kinabalu on 1 March 1968. He was appointed as Work Officer (Rural) and was moved to Beaufort District Office as Assistant District Officer (Rural) on 10 November 1969. He was loaned 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), Daawah Officer Islamic Council of Sabah (October 1986 until January 1988), Secretary of Islamic Council of Sabah (January 1988 until June 1994), Secretary of Home Affairs and Research (1994 to 1995) and Director in State Public Service Department (December 1995 to March 1998).
He was served as Deputy State Secretary (Administration) from 21 March 1998 until he retired on 8 December 2002. On January 1, 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.
