Luca Filippi will return to IndyCar to race a second Rahal Letterman Lanigan entry in the Houston and Toronto street course double-headers.
The 28-year-old Italian - a sometime Honda Formula 1 test driver and runner-up in the 2011 GP2 Series - came close to a deal with Bobby Rahal's team when he first tried to break into IndyCar two years ago.
That drive failed to come to fruition, although Filippi did make four IndyCar starts with Bryan Herta Autosport last year, taking best result of 10th in Houston.
"We tried to get Luca into the team a few years back and even went so far as to build a seat but we were unable to find the funding," said Rahal.
"In the meantime he went to Bryan Herta's team and showed what he can do in the few races he ran for them.
"He has been successful in GP2 in Europe, amongst other series, for a number of years so I don't think there is any question that he has the pace to run towards the front.
"On top of that, he is a real gentleman and we are looking forward to working with him and seeing how he can help the team progress."
After a tough start to the 2014 season, RLL took a breakthrough second place in the opening Detroit race with Graham Rahal a fortnight ago.
"I know the team is capable and has potential but it was good to see Graham on the podium in Detroit and so close to the win," said Filippi.
"That proved the car is working very well on a street course and I really expect to have a good feeling from the car again.
"We have been trying to find a way to work together for a long time and to finally have it happen is a great feeling.
"I really love the IndyCar Series. Since I first drove the car and experienced the atmosphere of the series, I have loved everything about it and can't wait to get back in a car."
Alongside Rahal, RLL also ran Oriol Servia in a second car in a limited programme in the early part of the season.