Vincent P. Greenwald, 63, a retired sales representative for the Xerox Corp. and an Army veteran of World War II, died of a heart ailment Friday at his home in Falls Church.

A native Washingtonian, Mr. Greenwald graduated from St. Paul's Catholic School here. During World War II, he worked as a heavy-caliber gun Technician at the Naval Gun Factory before entering the Army. He served at military installations in this country during the war and then with the Occupation Forces in Japan.

After his military service, he returned to the Washington area and worked as a sales representative for the Underwood Corp. In 1961, he joined Xerox, where he specialized in Navy accounts. He received many sales awards from the Xerox and Underwood corporations.

Survivors include his wife, Elizabeth H., of Falls Church; a son, Vincent P. Jr., of Arlington; a daughter, Janet Winslow of Sterling, Va.; two brothers, Richard and Emil Greenwald, both of Alexandria; a sister, Alice Sweeney of Glenmark Park, Md.; two half-brothers, Wilfred Boyce of Chicago, and Edward Boyce of San Francisco; a half-sister, Mary Williams of Kearneysville, W.Va., and two grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to charity.