The Briton, whose name wasn't reported, was receiving "appropriate care" and "consular assistance," the department said in a statement posted on its website Saturday.
"The overall risk to the public in the UK continues to be very low. Medical experts are currently assessing the situation in Sierra Leone to ensure that appropriate care is provided," professor John Watson, deputy chief medical officer, said.
"We have robust, well-developed and well-tested (National Health Service) systems for managing unusual infectious diseases when they arise, supported by a wide range of experts," he added.
This is the first case of a British national contracting the deadly virus in the current outbreak, the BBC reported.
Sierra Leone, Guinea and Liberia have been the epicenter of the recent Ebola outbreak, in which there are a suspected 2,615 cases and 1,427 deaths as of Friday.
No vaccine or cure currently exists for the flu-like virus, which causes fever with chills, joint pain, muscle pain and chest pain.
Since it was first discovered in 1976, the disease has infected fewer than 2,000 people, mostly in the tropical regions of Sub-Saharan Africa. It resides in infected pigs, monkeys and fruit bats, and can be transferred to humans.
In some cases there is up to a 90 percent mortality rate. The mortality rate of the current outbreak is a bit more than 50 percent.