"I'm not a hundred per cent, but Jenson was loyal when we were not doing very well. He has a lot of faith in us," the Briton, referring to the team's uncompetitive 2007 and 2008 seasons when owned by Honda, told Auto Bild.
Brawn, however, acknowledges that Button's value will surely increase if he manages to turn his current championship lead into the 2009 title.
In the throes of the management buyout last winter, the 29-year-old accepted a hefty salary cut as he was sure the BGP001 car would be a winner.
Brawn admitted: "Naturally I would offer him more money if he becomes world champion."
Regarding the occupant of the other seat, Brawn said he is not yet turning his attention to the 2010 driver line-up but he would be "content" to retain both Button and Rubens Barrichello.
He also said he is happy with the team's customer engine supplier.
"I hope we will cooperate with Mercedes for several years to come," said Brawn.