The pubs have reduced the price of a pint of real ale by an average of 20p.
More than 600 of the company’s pubs are now serving a pint of Ruddles (brewed by Greene King) for £1.69.
A further 160 pubs will be offering a pint for £1.59 or below, including 36 pubs which will be serving a pint for £1.39.
The remaining pubs will serve a pint between £1.99 and £2.89, depending on the individual pub’s location.
Wetherspoon chairman Tim Martin said: “At the current time customers and businesses pay tariffs on thousands of products which are imported from outside the EU.
“ These tariffs are collected by the UK government and sent to Brussels. Provided we leave the Customs Union on 31st October, the government can end these protectionist tariffs, which will reduce prices in supermarkets and pubs.
“In order to illustrate this point, Wetherspoon has decided to reduce the price of Ruddles bitter, brewed by Greene King.
“A lot of politicians have misled the public by suggesting leaving the Customs Union would be a ‘cliff edge’ or ‘disaster. This is the reverse of the truth. Ending tariffs will reduce prices.”