Three tiny Amur tigers were born at the Columbus Zoo and Aquarium in Powell, Ohio, late Wednesday night.
Video footage showed them snuggling up to their 11-year-old mom Irisa in a private den, away from the glare of visitors.
Zoo bosses said the trio, gender unknown, were being monitored via remote camera and "appear to be healthy."
"Welcoming tiger cubs at the Zoo is always exciting but it is also a time when we proceed with cautious optimism," zoo president and CEO Tom Stalf said in a statement. "Tiger cubs are very fragile at birth, however they appear to be thriving and Irisa is being an attentive mother."
The cubs' father is 8-year-old Jupiter, who arrived at the zoo from the Czech Republic last March as part of the European Endangered Species Program and the Association of Zoos and Aquarium's Species Survival Plan, which aims to increase the genetic health and diversity of tigers living under human care.
There are now seven Amur tigers at the Columbus zoo. However, fewer than 400 of the big cats, also known as Siberian tigers, are believed to be living in the wild in their native forests of the Russian Far East.
"Their populations are dwindling due to overhunting of prey species such as deer and wild boar, habitat loss and poaching for skins and body parts used in traditional Chinese medicine," the zoo said in a statement. "Humans directly cause 75 to 85 percent of tiger deaths."