NYU Langone Medical Center announced the Revlon Inc. chairman's donation Friday.
The new, 22,000-square-foot facility will more than triple the size of the old emergency department. It's been closed since the October 2012 storm.
The Manhattan hospital has since launched an urgent care center to help handle needs. That center is seeing at least as many patients as the old emergency department.
The hospital says that underscores the need for the upcoming Perelman Emergency Center. It's due to open around April.
The new facility will include more treatment rooms, plus dedicated space for pediatric emergencies.
The New York Times first reported the gift.