He died Saturday in Cincinnati at age 82.
No other information was released immediately, other than that the service would be private. A spokesman for his family said a public, national memorial service at another time is a possibility.
Ohio Sen. Rob Portman plans to speak at Friday's service. Portman has called the Ohio native "a good friend and adviser."
Portman is in Tampa, Fla., for the Republican National Convention. A spokeswoman says his office is working on travel arrangements to get him back to Cincinnati in time.
Armstrong commanded the Apollo 11 moon landing on July 20, 1969.