Northwich, built in 1898, is an unpowered narrow boat which would have been towed or pulled by a horse.
Steve Bagley, of the Canal and River Trust, said: "Caring for these vessels is not easy, their sheer size presents challenges."
Three other boats lifted from the docks are being put into storage.
Restoration work for the Northwich is being funded with a  Â£314,000 grant from Arts Council England.
Once the work is complete it will go on display at the National Waterways Museum in Gloucester Docks.
Northwich was built in Birmingham with an iron riveted side and elm bottom, which enabled it to carry up to 25 tonnes in cargo.
It was made for Nottingham-based transport company Fellows Morton and Clayton and worked on canals between London and Birmingham.
In later years it worked on the Trent and Mersey Canal, carrying chocolate for Cadbury's or aluminium for Rover in Wolverhampton, before it was used as a floating museum in Stoke Bruerne, Northamptonshire.
It was bought by the National Waterways Museum in 1988.
The oldest narrow boat in the Canal and River Trust's collection has been lifted out of Gloucester Docks to be restored and displayed in a museum.