In Washington, U.S. Rep. Carolyn Cheeks Kilpatrick told The Associated Press Thursday she "absolutely" would comply.
Notice of the subpoena was in Wednesday's Congressional Record.
Kilpatrick's office manager has also been told to appear at the grand jury. The dates of their appearances were not disclosed.
Federal authorities are investigating corruption in city government while Kwame Kilpatrick was mayor. He hasn't been charged in that investigation. He resigned in 2008 after pleading guilty to obstructing justice in a case that revealed his affair with his chief of staff.
His spokesman says he has no comment on the subpoena.
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Associated Press writer Erica Werner in Washington contributed to this report.