Frank O. Hewitt, 56, office manager and comptroller of the TJO Co., a building and construction firm in Arlington, died Tuesday at his Arlington home following a heart attack.

A native of Montgomery County, Mr. Hewitt was in automobile sales here and in Florida before joining TJO in 1977.

For the past 2 1/2 years, Mr. Hewitt also was involved in rehabilitation work with alcoholics. He was a trustee of Thomas H. Brown III & Associates of Arlington, an alcoholism counseling, rehabilitation and research firm and a nonprofit foundation.

He also worked as a volunteer in the alcoholic treatment unit at Arlington Hospital.

Mr. Hewitt, a longtime resident of Northern Virginia, was a graduate of George Washington High School in Alexandria.

He was a member of the Knights of Columbus.

Surivors include his wife, Lynn P., and his mother, Edmonia G., of the home in Arlington; a son, Stephen F., of Magee, N.C., two daughters, Carole Mitchell, of Fairfax, and Mary Hicks, of Charleston, W. Va.; a stepson, Brett Thompson, of Arlington; two step-daughters, Terri Garver, of Alexandria, and Dawn Thompson, of New York City; a brother, James T., of Winter Park, Fla., and two grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to Thomas H. Brown III & Associates, 5510 Columbia Pike, Suite 310, Arlington, 22204.