The exact cost of the mandatory fee has not yet been decided.
Entry to the memorial plaza with its twin reflecting pools will still be free.
The decision to charge for the underground museum housing relics of the Sept. 11, 2001, terror attacks has been met with dismay by some relatives of 9/11 victims.
Memorial foundation head Joseph Daniels said Saturday that the museum has little choice. It’s expected to cost nearly $60 million a year to operate the site.
Daniels said the museum will be free during certain hours every week.