Several caravans were seen pitching up on the ASDA car park in Westbrook, which is also home to Westbrook Library and St Philip’s CE Primary School and nearby church.
Six caravans were reported as making up the unauthorised encampment, which is believed to have arrived on Wednesday.
Police are due to attend to speak to the travellers on the privately owned land.
There have been a number of unauthorised sites established in Warrington in recent weeks.
This has prompted members of the public to question Warrington Borough Council over the location of the long-promised traveller transit site.
Funding to the tune of £2million was set aside as long ago as 2015 to assess the viability of creating a transit site in Warrington for the use of the traveller community.
As it stands, no such site has been created.
When asked by the Warrington Guardian for an update on the progress of finding a traveller transit site, a spokesperson for Warrington Borough Council said: “We remain committed to the delivery of a suitable transit site within the town and recognise the benefits for both the travelling community and our residents.
“We are continuing to work with our partners to identify a suitable traveller transit site in the borough.
“The need for this is fully established in the submitted proposed local plan that was subject to examination in public in September .”