Officials were still trying to determine how the attack happened because the beast was supposed to have been relocated to its nocturnal cage.
"We're going to find out what happened," said Lauraine Gagnon, the zoo's director general. "We'll look at all the procedures, how things are done with dangerous animals."
But she emphasized that the facility in Saint-Felicien, about 250 kilometres north of Quebec City, is safe.
"This is the first time this has happened in 53 years," she told a news conference. "But it's not something you want to have happen again."
Provincial police and Quebec's workplace-safety board were also investigating Thursday morning's incident.
Other employees at the zoo managed to rescue their colleague after the animal moved away toward another part of its habitat.
Gagnon denied that the animal had been shot.
She said there was no reason to kill the tiger because it was just acting out of instinct.
"For the moment, there is nothing that indicates the animal should be killed," Gagnon said.
The 51-year-old man is expected to survive, although he sustained deep wounds.
The incident is being investigated, with police also involved in case a criminal act such as negligence was committed.
Zoo officials have not decided what to do with the tiger.