The sanctuary, which lies close to Kosovo's capital Pristina, saw a 70% drop in visitor numbers in 2020.
The sanctuary's spokesman Jeton Hetemaj said they had been able to keep going thanks to the support of animal welfare organization Four Paws, based in Austria.
The 20 bears living at the sanctuary were confiscated from private owners or from restaurants where they were attractions for guests, the sanctuary says.
Hetemaj said the bears had been kept in spaces "as small as four or five square meters (43-53 square feet)" but the sanctuary has far larger enclosures imitating a natural habitat.
The bears are fed twice a day on a mix of fruit and vegetables and get meat three times a week, keeper Arben Bytyci said.
Although the sanctuary is open again to visitors, the numbers of people visiting are still smaller compared to before the pandemic hit, the sanctuary said.