Leonard Allen, 65, managing director of the Radio Television News Directors Association here and a retired NBC-TV news executive, died Thursday at Sibley Memorial Hospital after a heart attack.

Mr. Allen joined the association in 1976, after a long career with NBC's radio and television news divisions here and in New York City. He joined NBC in 1942 as a radio news writer in the international division, later become night news editor in the television division in 1952.In 1958, he became manager of television news reporting and subsequently served as manager of television foreign and domestic news.

In 1963, he transferred to NBC's Washington bureau as director of the news operation, a position he held for 10 years. He continued to live in the Washington area after returning to New York in 1973 as director of public affairs. He was an assistant bureau chief in New York when he retired in 1976.

Mr. Allen, who lived in Bethesda, was a native of New York City. He graduated from Cornell University and earned a master's degree from the Columbia University School of Journalism. He was a member of the Broadcasters Club.

He served as a sergeant in the Army for two years in World War II.

Survivors include his wife, Ruth Rose Allen, and a son, David, both of Bethesda; a daughter, Sherry, of Denver, and a sister, Irma Shepard of Los Angeles.

The family suggests that expressions of sympathy be in the form of contributions to the American Heart Association.