The pair will be making a return to the grid in 2026, after being dropped this year, for the American outfit, who become F1's 11th team on the grid.
Perez, the winner of six grands prix, was sacked by Red Bull as Max Verstappen's teammate at the end of last season despite two years of his contract still to run.
Bottas won 10 races at his time with Mercedes alongside Lewis Hamilton. The Finn raced for Sauber in 2024 and this term has acted as Mercedes' reserve driver.
Cadillac are looking to the two experienced drivers - both are 35 years old - to help them make a flying start to life in the fast lane.
Mark Reuss, the president of Cadillac's parent company GM, said the decision was based on the drivers' experience of wins and podiums in F1.
He described Cadillac's driver pairing as "a really good winning combination".
Dan Towriss, chief executive officer of GM's partner TWG Global, said: "Their experience, leadership and technical acumen are what we need.
"We're humbled by their belief in us and this project.
"There is a young pool of drivers who are exciting and very talented so it was a tough decision. But it was the leadership of these two drivers that stood out."
Perez said it was an "honour" to help Cadillac take their first steps in the sport.
"Cadillac is a legendary name in American motorsport, and to help bring such a fantastic company to Formula 1 is a huge responsibility, one I'm confident of taking on," the Mexican noted in the team's statement.
Bottas echoed his new teammate's excitement at the challenge.
"This isn't just a racing project; it's a long-term vision. It's not every day that you get a chance to be part of something being built from the ground up and helping shape it into something that truly belongs on the F1 grid."