Ganassi has confirmed that Ryan Briscoe will join the team in a fourth car for next month's Indianapolis 500, as predicted by AUTOSPORT last week.
Briscoe will drive the #8 entry alongside Dario Franchitti, Scott Dixon and Charlie Kimball in a deal that reunites him with the team that he began his IndyCar career with in 2005.
"To say that I'm excited for the month of May would be a huge understatement," said Briscoe.
"I'm thrilled to join the Ganassi team for the Indianapolis 500 this year. Driving for the defending race winner - and especially with team-mates that are former winners - is just incredible.
"There are still a lot of familiar faces on the team from when I drove for Chip in 2005, and I can't wait to get started. I'm looking forward to a successful month."
Team owner Chip Ganassi said that he expects the Australian to settle in quickly.
"We all know Ryan is a talented driver, having had him in our IndyCar system previously," he said.
"He will get up to speed quickly because he understands the ins and outs of how we operate our race programme. The opportunity to have him back in a fourth car with us alongside Dario, Scott and Charlie is big."
Briscoe started last year's Indy 500 from pole position, although his best result in the race is fifth. He has been out of a full-time drive since former employer Team Penske scaled down from three cars to two at the end of 2012.