The memorabilia, including some of the Paisley-born star's favourite instruments, are being sold by Rafferty's daughter Martha.
They will go under the hammer at Bonhams' in London tomorrow.
Fans all over the world, including America where Rafferty sold millions of records, have already expressed interest in the unique items.
But the handwritten lyrics to Rafferty's most famous hit Baker Street will not be sold.
Martha, 42, decided to keep them.