Elias William T. Whitlock, 89, a retired employe of the Post Office Department who was active in church organizations, died of cardiac arrest Sunday at the Carriage Hill nursing home in Silver Spring. He had lived in Washington since about 1920.

Mr. Whitlock worked for the Railway Mail Service for 35 years before retiring in 1955. While with the service, he spent 20 years as treasurer of the Postal Alliance Credit Union.

Mr. Whitlock had been a member of the Asbury United Methodist Church in Washington for 50 years. He had served it as a member of the church board and as church treasurer, as a member of the adult department of the church school and as a member of the Men's Club. He had been a lay delegate to church conferences.

In recent years, Mr. Whitlock had been organizing recreational activities at the Roosevelt Home for Senior Citizens in Washington, where he lived.

Mr. Whitlock was a native of Campbell County, Ky. He lived in Lynchburg, Va., before moving to Washington.

His wife, the former Laura Addie Williamson, died in 1954. Mr. Whitlock's survivors include a son, William Baldwin Whitlock of Washington; two daughters, Marian W. Carroll of Baltimore, and Nerissa Davis of Detroit; a brother, Seldon David Whitlock of Roanoke; four grandchildren, and three great-grandchildren.