Speaking on BBC NI's The View the DUP leader said: "We registered as a party in the Leave campaign because we felt very passionate about it.
"We played a role nationally.
"We received a donation which has been properly put into the Electoral Commission," she added.
Mrs Foster said she did not recall how much money was involved.
She declined to reveal the identity of the donor or donors but said the money was properly accounted for "under the rules as they currently stand".
Arlene Foster has confirmed that the DUP received a donation to advertise a pro-Brexit position in Britain prior to the referendum on the UK's membership of the European Union.