A native of Kingston, Ontario, McCreery holds a doctorate in Canadian history from Queen's University. His Master’s thesis, “Questions of Honour: Canadian Government Policy Towards Titular Honours”, was the first major academic work to examine the Canadian titles debate and the Nickle Resolution.
McCreery's published works include:
- "The Order of Canada; Its Origins, History and Development" (Toronto: University of Toronto Press, 2005)
- "The Canadian Honours System, 1st edition" (Toronto: Dundurn Press, 2005)
- "On Her Majesty’s Service; Royal Honours and Recognition in Canada" (Toronto: Dundurn Press, 2007)
- "The Maple Leaf and the White Cross; A History of St. John Ambulance and the Most Venerable Order of the Hospital of St. John of Jerusalem in Canada" (Toronto Dundurn Press, 2008)
- "The Beginner’s Guide to Canadian Honours" (Toronto: Dundurn Press, 2008)
- "The Authentic Voice of Canada: R.B. Bennett Speeches in the House of Lords, 1941-1947" (McGill-Queen's University Press, 2009).
- "The Canadian Forces’ Decoration" (Department of National Defence, 2010)
- "Canadian Symbols of Authority: Maces, Chains and Rods of Office" (Toronto: Dundurn Press, 2011)
- "Commemorative Medals of The Queen’s Reign in Canada, 1952-2012" (Toronto: Dundurn Press, 2012)
- "Maintiens Le Droit: Recognizing Service: A History of the RCMP Long Service Medal" (Royal Canadian Mounted Police, 2014)
- "Savoir Faire, Savoir Vivre: Rideau Club 1865–2015" (Toronto: Dundurn Press, 2014)
- "The Canadian Honours System, 2nd edition" (Toronto: Dundurn Press, 2015)
He also contributed a number of Commonwealth entries to Burkes Peerage and Gentry's "World Orders of Knighthood and Merit" (2006).
A number of chapters related to the role of the Governor General, reforms to the Canadian honours system and the modern role of the Provincial Lieutenant Governors were contributed by McCreery to “The Evolving Canadian Crown” (Institute of Intergovernmental Relations, Queen’s University, 2012) and “Canada and the Crown: Essays on Constitutional Monarchy” (Institute of Intergovernmental Relations, Queen’s University, 2013).
McCreery’s most recent works include:
- “The Order of Military Merit”, a work commissioned by the Department of National Defence to commemorate the fortieth anniversary of the establishment of the Order of Military Merit;
- “Maintiens Le Droit: Recognizing Service: A History of the RCMP Long Service Medal”, released in honour of the eightieth anniversary of King George V creating the RCMP Long Service Medal – Canada’s oldest long service medal; and
- “Savoir Faire, Savoir Vivre: Rideau Club 1865–2015”, a history of the Rideau Club.
- "The Canadian Honours System, 2nd edition" an greatly expanded version of the 1st edition 
McCreery is a Fellow of the Royal Canadian Geographical Society, a Fellow of the Centre for the Study of Democracy at Queen's University, a Fellow and Director of the Royal Heraldry Society of Canada, and a member of the Champlain Society, Orders and Medals Research Society, and the Canadian Historical Association. Since 2005, he has served as the National Historian for St. John Ambulance Canada and the Venerable Order of Saint John in Canada.
In February 2009, McCreery was appointed Private Secretary to the Lieutenant Governor of Nova Scotia. During the 2010 Royal Tour of Canada, he was appointed a Member of the Royal Victorian Order (MVO) by Queen Elizabeth II in Halifax.
McCreery previously served as a Senior Advisor to the Leader of the Government in the Senate, Marjory LeBreton (2007–2009); Senior Advisor to the Speaker of the Senate, Noel Kinsella (2006–2007); and Executive Assistant to Michael J. L. Kirby (2004–2006).
In 2010, McCreery was appointed by Prime Minister Stephen Harper to the Governor General Consultation Committee, a special committee convened to recommend a successor to Michaëlle Jean. The panel recommended David Johnston.
In November 2010, McCreery submitted testimony to the Senate Standing Committee on National Security and Defence outlining the way in which the Maritime Command element of the Canadian Forces could be renamed the Royal Canadian Navy. This advice was ultimately followed by Minister of National Defence Peter MacKay on 15 August 2011, when the designation Royal Canadian Navy was returned to official use, along with Royal Canadian Air Force and Canadian Army.
In April 2012, McCreery was appointed to the Board of Trustees of the Canadian Museum of History / Canadian War Museum for a four-year term.
- Newly Appointed Recipients of the Royal Victorian Order
- Governor General Consultation Committee