Since Nov. 1, adults without children may select items in the children's section, but they cannot read books or loiter in the department, said Marilyn Hoffman, a library spokesperson.
Officials with the Chicago-based Association for Library Service to Children said many libraries limit adults' use of computers or bathrooms in the children's departments, but Orange County's policy might be the first in the nation to restrict adults' presence in the areas.
"It's not a common trend, but I think it's going to become more common," said Cynthia Richey, a former association president. "It's, in part, a pre-emptive move."
Although Hoffman said no specific incident led to the new rules, Orlando police arrested a man in August after a 15-year-old girl said he tried to molest her at the downtown library.
Orange County, in central Florida, surrounds Orlando.