Pierre Kaffer with complete the United SportsCar Championship season with the Risi Competizione Ferrari squad.
The 37-year-old, who finished second in the American Le Mans Series GT2 class with the team in 2009, was brought into the Risi GT Le Mans class line-up to share its Ferrari 458 Italia alongside Giancarlo Fisichella at Laguna Seca at the start of May on a one-off basis.
Kaffer has now been confirmed as the permanent team-mate for the three-time grand prix winner after a successful test at Watkins Glen in May in preparation for this weekend's six-hour USC enduro at the track.
Kaffer, who finished third in class with Fisichella at Laguna, said: "After I did the test at Watkins Glen, it was a good surprise to receive a call to say that I would be racing for the rest of the season.
"It is satisfying that the team has put its trust in me."
The German takes the seat originally filled by Matteo Malucelli.
The Italian was banned from round three at Long Beach after an incident at the Sebring 12 Hours and was released by the team.