The woman was working in the big cat's enclosure at the South Lakes Wild Animal Park near Dalton-in-Furness last night, when she was mauled by the beast.
She was taken to Royal Preston Hospital suffering from head and neck injuries and the park has been closed.
Cumbria Police said that they are investigating the incident.
"The tiger is securely locked in its enclosure and there is no further risk to the public. Members of the public were not at any risk during the incident. The wildlife park has closed early and all visitors have left the park. Police and Barrow Borough Council are currently investigating the circumstances that led to this incident," said a police spokesman.
The wildlife park opened in 1994 and has both Siberian and Sumatran tigers.