The news put an end to months of speculation over where his future would lie following his shock resignation from his position as Red Bull's chief technical officer earlier this year.
Newey - widely regarded to be the sport's greatest designer - won 13 world championships during his time at Red Bull, working alongside the likes of Sebastian Vettel and Max Verstappen.
But one of the team's ambassadors has now revealed that there is work to do before the Brit officially takes up his role in early 2025.
Speaking on the F1 Nation Podcast, Pedro de la Rosa admitted: “The reality is that we are not ready for Adrian at the moment because our wind tunnel is still not working, but we are in a phase that in a few months, we will have our new wind tunnel, new simulator.
“We are not ready yet, but we will be in 2025 when he joins so that is the reality."
The former Jaguar and McLaren driver insisted however, that the team are in no doubt that they will be in a position to hit the ground running ahead of the start of next season.
“Also, he [Newey] knows better than all of us that Aston Martin will be ready when he arrives, and that’s why he’s joining," the Spaniard added.
“He would not join if he didn’t have the assurances or confidence that Aston Martin will be ready for him.”