Theodore Cabot Osborne, 89, a longtime contract lawyer with the Navy Department, died May 26 at Sibley Memorial Hospital in the District of cardiac arrest brought on by dementia. He was a resident of Washington for 60 years.

The greater part of Mr. Osborne's professional career was spent as counsel to the Department of Navy's Bureau of Ordnance, now called the Naval Ordnance Systems Command. He supervised the enforcement of government contracts and helped negotiate the sale of guided missile systems to the NATO Alliance. He received the Navy Superior Civilian Service Award for his service to the Navy. He retired in 1974.

Mr. Osborne was born in Cambridge, Mass., to a family that traced its New England lineage to the 17th century. He graduated magna cum laude from Harvard College and received a law degree from Harvard in 1940. He practiced law in Boston before enlisting in the Army in 1942.

He was part of the 10th Mountain Division, known as the Ski Troops, and served in the Aleutian Islands. In 1944, he was assigned to the Special Branch of the Military Intelligence Service at the Pentagon. In this position, Mr. Osborne worked in sensitive intelligence operations. He left the Army as a first lieutenant in 1946.

After the war, he worked briefly with the War Assets before taking his position with the Navy Department.

Mr. Osborne's interests included skiing, sailing, cabinetry and landscape design. He was an accomplished guitarist and, in his youth in Boston, was a member of a choir that sang the music of Bach. He was a member of the Army and Navy Club, as well as St. John's Episcopal Church in Washington, where he was head usher. He and his wife traveled widely throughout Europe and Asia and visited every state of the union except Alaska.

Survivors include his wife of 56 years, Elva Lenz Osborne of the District; one son, Theodore Cabot Osborne Jr. of Alexandria; and one grandson.