Jaime Camara has replaced Franck Perera at Conquest Racing ahead of the fourth round of the IndyCar Series at Kansas Speedway which takes place this weekend.
The 27-year-old Brazilian will occupy the seat alongside Enrique Bernoldi for the rest of the season.
Camara has tested IndyCars extensively for Andretti Green Racing over the past two years and has completed three years in the Indy Pro Series - two of them with AGR.
"It's a great opportunity for me to be driving for Conquest Racing," said Camara. "It's been hard work since 2005 when I came to the United States to race. It's just a dream come true.
"My goal was always to go to IndyCar, I never looked at going to Europe to try different series, it was always here. It's a good feeling that I have now, I am happy that it happened with the merger going on because now all the teams are here and the Series is gaining momentum and that's going to be great."
Conquest Racing Team Owner Eric Bachelart commented: "Jaime will be a great addition to our team. With his oval experience and Bernoldi's road, street course experience it will be a good combination.
"Jaime has proved himself in Indy Lights and I think he will fare well in the IndyCar Series."
Bachelart added that he was sad to have lost the services of former GP2 Series driver Perera, who finished a creditable sixth in last weekend's Champ Car finale at Long Beach.
The 23-year-old Frenchman lost his drive after Conquest sponsor Opes Prime went into receivership, and Perera's backer ARES withdrew.
"He [Perera] has done exceptionally well in his IndyCar Series debut as well as in his one and only Champ Car race and we are keeping him as our reserve driver for the remainder of the year but he will be released should a racing seat be available for him with another team," said Bachelart.