American Alexander Rossi has been named Manor's official reserve driver.
Rossi, 24, will combine his duties with his first season in the IndyCar series in the US, attending 11 grands prix.
Racing director Dave Ryan said Rossi had been kept on after racing for the team in five races last season because they needed "a safe pair of hands".
Ryan said the reserve role "always carries the potential to step up to race".
He added: "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."
Rossi said: "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.
"It was disappointing to miss out on a race seat with Manor Racing this year; everyone knows I pushed and worked hard for it.
"I'm confident this experience will add to my role as a very important cog in an F1 team's wheel."