The 28-year-old made 117 appearances for Leeds over three seasons, having initially joined on loan from Torino.

Jansson played 41 times in 2018-19 but missed Leeds' play-off semi-final defeat by Derby through injury.

Bees head coach Thomas Frank said he will bring "immense professionalism and experience" to his side.

"To have someone with his CV turn down other offers to join us shows where we stand as a club now," he added.

Brentford have the option to extend Jansson's contract by a further year.

"It was only very recently that we were alerted to his availability and reacted quickly to the opportunity," said the club's co-director of football Phil Giles.