Leanne and George, the Sumatran tigers, have three cubs, not just one.
The zoo keepers didn't want to get too close to the tiger family to count the babies, which had been born last week.
But when the mama cat got up to get a drink, the zoo keepers noticed three cubs in their nesting box.
The zoo people are monitoring the tigers via audio and video feeds.
The zoo keepers say Leanne is taking good care of her cubs.
The vets expect to give the babies a physical in the next few days.