The son of Dean Conrad Allard, Sr., and his wife Elizabeth Donaldson Graves, Allard atteded the Pembroke Country-Day School in Kansas City and then went on to Dartmouth College, where he earned his A.B. degree in 1955 and was elected to Phi Beta Kappa. He married Constance Lynne Morgan on June 17, 1955, with whom he had three children.
Upon leaving active service in the Navy, Allard was appointed head of the U.S. Navy's Operational Archives in 1958 and served in that position until 1982, when he became senior historian. In 1989, he was appointed Director of Naval History and served in that capacity until his retirment in 1995.
Allard served as an adjunct professor of history at George Washington University from 1979 to 1989. In addition, he served as President of the Arlington Historical Society from 1974 to 1975; member of the council of Woodlawn Plantation in Fairfax, Virginia, from 1976 to 1984; chairman of the Historical Commission of Arlington, Virginia, from 1978 to 1980; and member of the French-U.S. Scientific Committee on the CSS Alabama from 1991 to 1995.
U.S. Naval History Sources in the Washington Area and Suggested Research Subjects, compiled by Dean C. Allard and Betty Bern. Washington; U.S. Govt. Print. Off. 1970.
The United States Navy and the Vietnam Conflict: The Setting of the Stage to 1959 , vol. 1. by Edwin B. Hooper, Dean C. Allard, and Oscar P. Fitzgerald. Washington; U.S. Govt. Print. Off., 1976.
U.S. Naval History Sources in the United States, compiled and edited by Dean C. Allard, Martha L. Crawley, and Mary W. Edmison. Washington; U.S. Govt. Print. Off. 1979.