Alexander Rossi has been named as Manor's reserve driver for the 2016 Formula 1 season.
The American missed out on a race seat with the outfit to Rio Haryanto and subsequently signed a IndyCar deal with Andretti Autosport.
On Wednesday, Manor announced that Rossi would dovetail his IndyCar duties with the F1 reserve role that will see him attend 11 grands prix.
"I've invested most of my career in F1 and I'm not one to kick my heels and wait for things to happen, so this is my way of staying sharp and prepared," said Rossi.
"It was disappointing to miss out on a race seat with Manor Racing this year; everyone knows I pushed and worked hard for it.
"As official reserve driver though, I have a very complimentary dual program at the highest level of motorsport.
"IndyCar Series is the premier category of open wheel racing in North America and extremely competitive.
"My schedule this year is demanding, but no more than a full-time F1 schedule.
"I will attend 11 grands prix, only five of which take place during the IndyCar season, and I am certainly used to the travel demands of the F1 calendar."
Having filled test and reserve roles with Caterham and Marussia between 2012 and '14, Rossi made his full F1 debut in last year's Singapore Grand Prix.
Stepping in for Roberto Merhi as part of a five-race Manor deal alongside his GP2 campaign, Rossi's best finish was 12th in the United States Grand Prix.
"We need a safe pair of hands for the role, which always carries the potential to have to step up to race, but also someone who can really contribute to the development of the car," racing director Dave Ryan said.
"For Alex, F1 is still unfinished business.
"He did a great job when he drove for us in five of last season's races and he's a highly rated and valuable part of our line-up.
"He does have one heck of a schedule ahead of him and it's a commitment that only the most disciplined of drivers would be able to manage.
"We're confident he's the man for the job."