Earlier this year, the former Big Bang Theory actor had stopped appearing on the popular game show show after declaring her support for the Hollywood writers' strike.
Bialik is a neuroscientist and former star of The Big Bang Theory. Jennings is a former Jeopardy! contestant who went on an unmatched 74-game winning streak and was a consulting producer on the show.
"There will only ever be one Alex Trebek, but I'm honored to be helping Jeopardy! out with this in January," said Jennings, one of the show's all-time top winners.