Giuliano Salvi, who now works alongside Magnussen at Haas, has previously race engineered at Ferrari for the likes of Michael Schumacher, Felipe Massa, Fernando Alonso and Raikkonen.
But he said Magnussen, 24, most reminds him of the Finn.
“He is very honest and direct, which I really like,” Italian Salvi told Ekstra Bladet newspaper.
“As a character, Kevin reminds me of Kimi a lot. They are both Nordic, who are — how should I say it? They do not care about politics and they have no facade.
“The first impression may be misleading, because they struggle to have an immediate connection with you. But when you work with them, and get to know them a little deeper, they are really open,” he added.
“They are like cats,” Salvi continued. “If they are afraid, you see it. If they are angry, you see it. And that is really good. You know how they think and feel.
“You never leave a meeting with Kevin and think ‘He said one thing to me but he may mean something quite different’. No, he said it because he believes it.”