Upon graduation, Cabot started working for Cabot Corporation, founded by his father. He was CEO of Cabot Corporation from 1922 to 1960, when he relinquished active control of the company, and went to his Boston office as director emeritus on a regular basis until his death. Cabot was also a longtime director of United Fruit Company, and became its president in 1948 in hopes of reformation, but resigned in 1949. His brother John Moors Cabot was a major shareholder of United Fruit, as was another family member, Henry Cabot Lodge, Jr., who also served as a director of United Fruit. In 1951, Cabot was U.S. Department of State's Director of Office of International Security Affairs during the Truman administration, where he spoke for the State Department on NATO affairs, was in charge of a U.S. program arming allies throughout the world, and supervised the disbursement of $6 billion in foreign economic and military aid. In 1953, he also served as consultant on a special development mission in Egypt. In 1960, a Central Intelligence Agency cover called Gibraltar Steamship Company owned and established Radio Swan on Swan Island, a covert black operation to win supporters for U.S. policies and discredit Fidel Castro. Cabot, his brother John Moors Cabot, another family member Henry Cabot Lodge Jr., and Cabot's son, Louis Wellington Cabot, were all Council on Foreign Relations members inducted in 1992.
Philanthropic work
Cabot also served on the Harvard Board of Overseers, was a Director of the Harvard Alumni Association and significant benefactor of the university, and recipient of a Harvard Medal and honorary Doctor of Laws degree in 1970. In 1985, Harvard's Cabot House was named in honor of Cabot and his wife. The Cabot Science Complex is also named in their honor.
Writings
Quick-Water and Smooth: A Canoeist's Guide to New England Rivers, 1935
Cabot was married to Virginia Wellington Cabot for 75 years, from 1920 to his death in 1995. They resided in Weston, Massachusetts for seventy-five years, and had five children: Louis Wellington Cabot, businessman, philanthropist, former Chairman of Federal Reserve Bank of Boston, Thomas Dudley Cabot Jr., Robert Moors Cabot, Dr. Edmund Billings Cabot, Andover star and retired surgeon, and Linda Cabot Black, cofounder of Opera Company of Boston and Opera New England. in his 80s he lost the sight of an eye in a cross-country skiing accident, but he retained his enthusiasm for the active life. He and his wife, who celebrated their 75th wedding anniversary were tramping the mountains of Colorado. They also had 29 grandchildren, and 23 great-grandchildren. Virginia Cabot died in 1997 at Phillips House in Massachusetts General Hospital in Boston. She was 97.