Hangeland is out of contract at the end of the season and the 31-year-old has been linked with a move to Fulham's local rivals Queens Park Rangers.
The Norwegian defender has made over 220 appearances since joining Fulham from FC Copenhagen five years ago and Jol hopes the signings of the likes of Dimitar Berbatov will have convinced Hangeland of the club's ambition.
"We will try to do everything that we are capable of to keep him," said Jol. "There is a contract and the only thing for him to do is sign it.
"Players like Brede, if they have a decent history and are playing well for their clubs, then there will always be an interest.
"I thought he was quite happy to stay here. Of course, he wanted to know the mission of the club, who is coming in because there were quite a lot of players going out.
"Then Dimitar Berbatov, Mladen Petric and Hugo Rodallega came in and he was quite happy, but now it is three months on.
"There is still five months left and hopefully he will put the money where his mouth is, show everyone he is happy again and sign the contract."