ST. PETERSBURG, Fla. -- Justin Wilson says his extended offseason was a test of his resolve and commitment to motorsports in general and the Verizon IndyCar Series in particular.

Now Wilson, who last competed in an IndyCar last August to close the 2014 season, will make his 2015 Verizon IndyCar Series debut in an Andretti Autosport car in the Angie's List Grand Prix of Indianapolis on May 9 and also compete in the 99th Running of the Indianapolis 500 on May 24, the team announced.

Wilson, 36, who has seven victories and 26 podium finishes in 11 Indy car seasons, will drive the No. 25 Honda.

"It's a great opportunity. That was the one thing, when I look back, how do I want to plan my future and what's the next career move," said Wilson, who drove for Dale Coyne Racing the past three seasons. "It's been a rollercoaster of an offseason. I just had to keep pushing on, keep being determined to be here, trying to make something happen. It's frustrating, but what else can you do? You can either give up and quit and leave, or you can keep pushing, try and fight for a place to be here on the grid.

“It's nice to know you have something to focus on, something to work towards, and you've got a date for that. This whole offseason I've been training as hard as ever at the gym, on the cardio. I know driving these cars with this extra downforce is going to be more physical. I didn't know if I was going to be in or not going to be in. But you've got to be ready for whatever opportunity comes along. I'm looking forward to continuing my relationship with Honda and to working with Ryan (Hunter-Reay), Carlos (Munoz) and Marco (Andretti). I know that the team has everything in place to do well, and I'm really confident about what the group is capable of this year.”

In seven Indianapolis 500 starts, Wilson has three top-10 finishes with a best of fifth in 2013. He qualified 14th the past two years. He most recently competed last weekend in the 12 Hours of Sebring for Michael Shank Racing, which he co-drove to victory for in the 2012 Rolex 24 Hours At Daytona.

“We are so happy to be able to confirm Justin has joined our IndyCar program for both races at the Indianapolis Motor Speedway,” said team owner Michael Andretti. “Having Justin on the team has been something we’ve been looking at for quite some time, so we’re excited to finally make it happen. We have a lot of (sponsorship) irons in the fire to get him in the car a lot more.

"Adding him to the roster for the Indy races is definitely going to be something special as we work to defend our 2014 victory.”

Hunter-Reay won the Indianapolis 500 in the No. 28 DHL Honda.

Simona de Silvestro is driving the No. 25 entry in the season-opening Firestone Grand Prix of St. Petersburg on March 29. Andretti said his goal is to run five cars at Indianapolis.

"Just like Justin, we are pushing hard on that front to get her in a car for more than just this race. We're hoping we can put something together and announce something soon," Andretti said. "We're excited to have her on the team. She just did her first test (with the new Honda aero package at Sebring International Raceway earlier in the week) and everyone that was at the test was impressed with not only what she did on the track but what she was able to offer outside of the car. We're all really pumped for this weekend."