Happy Endings inherited the 21 birds after a request from their owner, who died after a battle with cancer this summer.
The charity say they would not survive in the wild, so this group of owls, known as a Parliament, will be kept at the centre in Well Lane, Ospringe for life.
But now the volunteers are facing a race against time to find £5,000 to pay for the giant aviary it has built to house them.
Happy Endings co-founder Chris Johns, 25, said: "Twenty one owls is certainly one of the more unusual new arrivals we have had to help but they are enjoying stretching their wings and settling in here at Faversham.
"The owls were born in captivity so releasing them into the wild was never an option, they would not survive. Instead, they have a have home for life here with us and the rest of our animals."
In captivity barn owls can live for more than 20 years and although they are Britain's most common species of owl, the UK population is falling due to loss of habitat and prey.
The owls, which are all related and are aged from 12 to 17 years old, had previously been kept as pets in the garden of a home near Hawkinge.
They were brought to the rescue center in cat boxes after the owner died.
Mr Johns continued: "We will have to continue fundraising to pay for the aviary, but saving these birds was our priority and also giving their previous owner peace of mind.
"We don't have any space for more birds at the moment but in the future we would be able to use the aviary to home other rescue birds, giving them space to fly and an experience as close to being in the wild that they can get in captivity."
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