During World War II, Sydnor served in the United States Navy aboard three destroyers, last holding the position of First Lieutenant.

Sydnor was the president and significant stockholder of Southern Department Stores (now defunct but then with 20 retail locations in Virginia and North Carolina, including in Williamsburg, Gloucester, Petersburg, Rappahannock and Kilmarnock).

In 1951, the National Labor Relations Board ruled against the family's Richmond Dry Goods Co., which was the target of unionization efforts.

In that election, W. Moscoe Huntley, Fred G. Pollard, W. Griffith Purcell and J. Randolph Tucker Jr. were re-elected, but Sydnor, George E. Allen Jr and Edward E. Lane replaced William H. Adams, Albert Orlando Boschen and Charles H. Phillips.

[11] Sydnor did not seek re-election in 1959 (the first year in which the senatorial districts were numbered), and Bemiss also succeeded him in the Virginia Senate representing Richmond along with Haddock and Willey.

In the 1970s, Eugene and Lucy Sydnor had acquired an estate at "Dancing Point" in Charles City County overlooking the confluence of the James and Chickahominy Rivers.

In March, 1999, the family store in Williamsburg, run by his son Charles, requested bankruptcy court protection, in part due to ice storm damage.