Bourdais will team up with Sebastian Buemi this season
Frenchman Sebastien Bourdais has earned a second year at Toro Rosso, reducing British driver Jenson Button's hopes of staying in Formula One.
The 29-year-old Bourdais had spent an anxious winter waiting while the team assessed alternatives.
But he was confirmed as team-mate to rookie Sebastian Buemi on Friday.
Button was one of those linked to Toro Rosso and their decision means the Englishman's hopes rest with a rescue package for the collapsed Honda team.
Honda quit F1 in December, citing falling car sales and the global financial crisis.
Toro Rosso team principal Franz Tost said: "We expect him [Bourdais] to profit from the experience he gained last season.
"He now knows the F1 environment, tracks and the team and the return of slick tyres should suit his driving style."
After 11 years using grooved rubber, slick, untreaded tyres, are being re-introduced to F1 this season among a raft of other rule changes aimed at improving the quality of racing.
Bourdais was overshadowed for much of last season by former team-mate Sebastian Vettel, who has been promoted to the main Red Bull team alongside Mark Webber for 2009.
And Bourdais, a four-time winner of the US-based Champ Car series, admitted his relief at finally securing the drive.
"It has been a very long and difficult winter, but now the waiting is finally over and I am really excited about tackling my second season with Scuderia Toro Rosso," he said.
"Now I can focus on preparing for the coming season. It promises to be a very interesting one, thanks to all the rule changes."
Red Bull launch their new car in Jerez in Spain on Monday, ahead of a major three-day test involving many of the leading F1 teams.
Toro Rosso will use the same car as Red Bull, but fitted with a Ferrari engine rather than the Renault used by their parent team.