Despite having recently extended his contract at the Champions League semi-finalists, Upamecano continues to be linked with a move to Manchester United.
Although Nagelsmann has acknowledged that a transfer could occur in 2021, he has said that the France international will spend the 2020-21 campaign in Germany.
Speaking to ESPN, Nagelsmann said: "He will be here for the season. I'm sure about that. As for the future, I'm not sure as he is very talented.
"Lots of clubs will want to buy - next season it could be real that he leaves the club. But this season he will stay."
The 21-year-old has made 113 appearances in all competitions since his move to Leipzig in January 2017. body check tags ::