In a 6-1 vote Tuesday, the Key West City Commission banned the sale of sunscreens using oxybenzone and octinoxate beginning on Jan. 1, 2021.
Mayor Teri Johnston said it's the commission's "obligation" to protect the reef, which is the only living coral barrier reef in the continental U.S.
Researchers say the chemicals lead to bleaching, DNA damage and death of the corals.
The vote followed an hour of public comment, with almost every speaker supporting the ban.
Commissioner Greg Davila dissented, saying residents should have the choice of sunscreens they want to use.
Last year, Hawaii banned sale and distribution of similar sunscreens beginning in 2021.