The French champions have already lost Tiemoue Bakayoko, Benjamin Mendy and Bernardo Silva to Chelsea and Manchester City.
Meanwhile, Arsenal have had two bids for Lemar turned down but are expected to return with a third which could be in the region of £50million.
Interest in Mbappe, Thomas Lemar and Fabinho has intensified over the summer.
"All the players who were important last season are important to keep for the club", he said.
The 21 year-old has signed a five year contract with the Ligue 1 club, and he was quoted on the Monaco official website as saying: "I'm very happy to join Monaco, a club with a very ambitious sporting project who field a lot of young players".
However, despite the speculation surrounding Mbappe and Lemar's futures, Jardim has admitted they are still behaving like consummate professionals.
'So our goal is to work well with players who will stay here after the transfer window closes.
He continued: "It's not only about [Kylian Mbappe], all the young players who were here a year ago and had a great season".
"Fabinho, Lemar, Kylian, we're talking about them joining other clubs, but they stay focused". They know that the most important thing is the pitch'.