Cook is closing in on his 10,000th run in the format, heading into the second Test against Sri Lanka at Durham just 20 runs short of the landmark.
Former India batsman Tendulkar currently leads the way with 15,921 runs to his name, but Flintoff sees no reason why his former teammate can't break that record.
"Can he catch Tendulkar? Why not? At a similar age a couple of years ago he had a better record than Tendulkar," he told PA.
"He's only 31 so he's got years ahead of him. He can go on another five or six years. But the good thing about Alastair is he won't be looking at that. He'll be looking at where he can take this team.
"He's not into personal milestones. When he gets to 10,000 runs he'll get a nice clap from the crowd and raise his bat, but he'll be more focused on the next ball. He's a selfless cricketer."
England's second Test against Sri Lanka starts on Friday.