Kniazieŭ began his career as a mechanic at the Sibselmash plant. He headed the military counter-intelligence unit of the Belarusian KGB and the Institute of National Security of the Republic of Belarus.
On 6 February 2001 he was appointed Deputy State Secretary of the Security Council of Belarus.
On 6 August 2001 he became First Deputy State Secretary of the Security Council of Belarus.
On 12 September 2001 he was appointed First Deputy Head of the Presidential Administration of the Republic of Belarus.
On 25 March 2003 he was appointed rector of the Academy of Public Administration.
Since 3 September 2011, he has been rector of MITSA International University.