The mad-keen Sheffield United fan has donated a signed, framed shirt to the Save Our Millers fund, backed by The Star, which has also been autographed by Neil Warnock and the entire Blades team.
The shirt is currently up for auction on Internet auction site Ebay at a starting price of £300.
The cash-starved Millers have set a target of raising £1 million by March 25 to stave off closure - and have so far raised more than £265,000.
Millers fundraiser Mick Mills, of Maltby, whose network of friends includes a pal of Sheffield-born Sean, persuaded the movie star to support efforts to save Rotherham United from going under.
Mick said: "Sean came into the country to watch the Blades play against Crewe.
"A mutual friend accompanied him to the match and asked if he could help me out with my fundraising events. To his credit, he generously donated the shirt after he had got the team and Neil Warnock to add their signatures."
A staunch follower of Rotherham United, Mick has organised charity auctions to help the Save Our Millers campaign and is currently arranging a race night at Maltby Miners' Institute tomorrow.
"I cannot believe how kind this is as a gesture. Sean is typical of so many Sheffield fans who have shown compassion for the Millers plight," added Mick.
"This kind of attitude shows we can all pull together and recognise the importance of saving the Millers."
The Ebay auction for the framed shirt, which features the message 'Good Luck To The Millers', ends on Monday at 4.49pm.