The grand jury had been considering the case since shortly after the March 29 incident, which has led to much discussion on Capitol Hill about race and the conduct of lawmakers and the officers who protect them.
"We respect the decision of the grand jury in this difficult matter," said U.S. Attorney Kenneth Wainstein.
His statement, released late Friday, also included support for the officer involved, Paul McKenna, and the Capitol Police. He said, "This is a tremendously difficult job, and it is one that Officer McKenna and his colleagues perform with the utmost professionalism and dignity."
With that, Wainstein closed a case that has simmered with racial and political tension.
"I am relieved that this unfortunate incident is behind me," McKinney said in a statement Friday night. "I accept today's grand jury finding of 'no probable cause' as right and just and the proper resolution of this case."
The encounter began when McKinney, D-Ga., tried to enter a House office building without walking through a metal detector or wearing the lapel pin that identifies members of Congress.
McKenna did not recognize her as a member of Congress and asked her three times to stop. When she ignored him, he tried to stop her. McKinney then hit him.
McKinney described the encounter as "racial profiling," insisting she had been assaulted and had done nothing wrong.
McKinney is black. McKenna is white.
Others noting McKinney's non-indictment: Stop the ACLU, Hot Air, Sister Toldjah, and Outside the Beltway.