About 260 signs were given to the Friends of Ceredigion Museum in order to raise money for renovations.
The road signs were replaced as part of an Â£800,000 scheme to improve the look of the Welsh seaside town.
The value of the "unique" signs has not yet been confirmed but they will go under the hammer from 19:00 GMT at The Coliseum in Aberystwyth.
Mona Morris, president of the Friends of Ceredigion Museum, said: "We've already had lots of interest in the road signs from local people and businesses.
"The signs are a unique bit of history that really evoke a sense of place."
The auctioneer on the night will be local hotelier, Geraint Hughes.
"It'll be fun to wield the hammer again," the former auctioneer said.
Old Aberystwyth road signs will be auctioned on Monday after being replaced with Edwardian-style versions.