The incident involved a female worker at the Topeka Zoo and was witnessed by some visiting the facility.
The tiger that attacked the keeper, a seven-year-old male named Sanjiv, did so after she entered his outdoor habitat at around 9.15am.
The zoo was closed for 45 minutes after the attack.
Its six tigers, including Sanjiv and his four cubs, were kept in their pen after the incident.
All the tigers except Sanjiv were later allowed back to the outdoor exhibit area, though zoo officials did not plan any repercussions for Sanjiv.
"There was some sort of error that occurred here," zoo director Brendan Wiley said, adding that the incident was under investigation.
"Some of our staff witnessed some things that you hope you go through a career without witnessing.
He added: "Sanjiv this morning did exactly what a tiger would when something comes into his territory."
He said there was "absolutely no consideration to euthanise Sanjiv".