The red pandas were born in late June, but the Kolmården zoo kept the secret until Monday.
"This birth has been a long time coming, because Pandora gave birth to this pair a fortnight later than the one she had last year," a spokesperson said.
"Each day we had our fingers crossed that something would happen until one day we finally heard a baby squeal - it sounded like a bird tweeting."
Each of the red pandas weighed 100 grammes at birth, but have already shot up to 500 grammes each, and they're expected to grow to be five kilogrammes.
The panda parents, Pandora och Maïko, were born in France and came to Sweden's Kolmården in 2011.
Those keen to see Plopp and Polly in real life will have to wait until the end of August.
Red pandas, which are native to Asia and also known as lesser pandas, are an endangered species. There are an estimated 2,500 in the wild.