American Scott Speed will race for Toro Rosso again this season, the F1 team said in a statement.
The announcement completed the starting grid for the championship, which starts in Australia on March 18.
Ferrari-powered Toro Rosso had already confirmed Italian Vitantonio Liuzzi as their other driver.
The 24-year-old Californian's future had been uncertain after team co-owner Gerhard Berger said this month that contractual issues remained to be sorted out between the driver and team.
However, the only American Formula One driver took over from Liuzzi for the third day of testing with Toro Rosso in Bahrain on Saturday and completed 60 laps.
Double world champion Fernando Alonso lapped quickest for McLaren, ahead of rookie British team-mate Lewis Hamilton.