In a letter Derek Andrew, Managing Director of Wolverhampton-based Marston's, said that "this gesture is from the hardy football supporters among us".
Mr Andrew, a Wolves fan, said that Marston's general stance on fundraising was normally to support disadvantaged individuals or groups but on "this occasion I am happy to enclose a cheque for £500 to help towards your target."
He has also invited the appeal committee to take part in joint activities in the future with Marston's.
David Craig, appeal project manager and a member of the board of Cardiff City Supporters' Trust, said: "This is a great gesture from Marston's and we're delighted because the pub and restaurant is based just yards from where the statue of Fred Keenor will be sited.
"We'd like to see businesses and employers in South Wales, particularly those with links with Cardiff City, following the lead set by Marston's, which is, after all, a business based in the West Midlands.
"The donation from Marston's means we have now passed £47,500 on our way to the £85,000 needed."
Earlier this year Cardiff City Supporters' Trust wrote to Mr Andrew urging him to consider naming the pub, which is at the junction of Leckwith Road and Ffordd Fred Keenor, after the Cardiff and Wales skipper, who led Cardiff City to FA Cup triumph in 1927 the only time the trophy has been taken out of England.