Thomas G. Heffernan, 64, a mortgage banker with the Madison National Bank and the United Virginia Mortgage Corporation died of leukemia Sunday at the Fairfax Nursing Center.

A native of Bayonne, N.J., and a graduate of the American School of Banking in New York City. Mr. Heffernan worked as a mortgage banker in New York for 35 years. He began working with the American Bankers Association in 1960 and transferred to its Washington office in 1970. A year later, he joined the Madison National Bank as a vice president of the mortgage department.

He remained at the Madison National Bank for five years before becoming a construction loan officer with the United Virginia Mortage Corporation in Alexandria. He retired from there last October because of illness.

Mr. Heffernan a member of the National Mortgage Bankers Association, the Society of Real Estate Appraisers, the American Legion Peter Minuite Post No. 1247 in New York City and the Knights of Columbus Council, No. 4522.

Survivors include his wife, Paula C., of the home in Springfield Va.; two sons, Thomas J. of Jacsonville, Fla., and Robert F., of Plainfied, N. J., two brothers and three sisters, all of New Jersey, and three grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.