Travellers were moved on from Waterhall Golf Course yesterday and set up camp in Surrenden Park in Brighton.
A group of 11 caravans turned up at about 9am.
The gate to the field was wide open, though the council says it was secured overnight.
Brighton and Hove City Council has confirmed the unauthorised encampment and has visited the site with the police to carry out a community impact assessment.
A Brighton and Hove City Council spokeswoman said: “There was damage to the gate so it looks like a break in.
“Our traveller team has visited and is in discussion with the police on next steps.”
Yesterday’s encampment follows one which appeared on the same field in early May.