Blackadder has signed a one-year contract extension until June 2020.
The Premiership club have also confirmed former captain Stuart Hooper will become Blackadder's successor when the New Zealander decides to move on.
First team coaches Toby Booth and Darren Edwards will leave the club at the end of this season.
Former All Blacks captain Blackadder, 47, originally signed a three-year deal at The Rec when he joined in 2016.
In a lengthy open letter to Bath supporters, chief executive Tarquin McDonald laid out the club's long-term plans.
