The forward, 21, received an England call-up earlier this week after an impressive start to life at Stamford Bridge where he has contributed six goals and four assists in 14 games.
He arrived in the summer from Manchester City for £42.5million having come through the academy set-up at the Etihad.
The attacker made 41 appearances for Pep Guardiola’s men, scoring six goals and providing two assists.
But he was an admirer of rivals Manchester United when he was a boy – despite going on to be on Man City’s books for 15 years.
Palmer was pictured in a Red Devils shirt as a youngster and has now revealed he idolized Wayne Rooney when he was growing up.
He said: “What a player. When I was growing up I used to watch all the football and the one that sticks in my mind is Rooney.
“Ever since I was a little kid he has been my footballing hero.”
Palmer could make his international debut against Malta at Wembley on Friday evening or away in North Macedonia on Monday.
And he has admitted his recent rise has taken him by surprise.
He added: “Yeah, it’s been crazy. The changes have happened so fast.
“From winning the Euros with the Under 21s to signing for Chelsea, then getting called up here. It’s all happened so fast. I am excited for it all.
“In the garden as a kid, I used to pretend to be loads of players. Rooney, Ronaldo, Messi. All of them.
“But all this felt a long way away when I was that age.”
He also opened up about the adjustment he has had to make after swapping Manchester for London.
He said: “It was a big move for me. I’d never been out of Manchester, not even on loan or anything.
“So to move down to London on my own was a big thing. When I first went down there it was difficult. I was staying in a hotel but now I have settled in more and I’m enjoying it.
“It happened fast. I thought for my career I had to go and get regular game time. The competition that’s there at City, it was going to be hard.”