Thirty-one-year-old Tremlett was named in the England performance squad last week following a lengthy battle with a back injury.
With New Zealand, Australia and the Champions Trophy to come this summer, Cook has admitted that the bowler will provide him with a "different" option.
"We saw in Australia, when he was fully fit, what he can bring to any bowling attack, his line and length there were pretty much immaculate throughout those three Test matches he played and he became very hard to score off," said Cook.
"It's great to see him back fit. He's obviously got to play a lot of cricket again to get up to the rigours of bowling, especially if you're going into any Test match with a three-man seam attack, you've got to be pretty confident that all the guys will get through.
"He's got a lot of work to do and he knows that. But he brings something different which not many other bowlers in the world do."
Tremlett was part of the England bowling attack that helped the nation win the Ashes back in 2011.