Police officers are patrolling Horsham Park after a large group of travellers moved in.
The travellers took up residence in the park after they were evicted from Victory Recreation Ground.
But Horsham District Council said West Sussex County Council is serving the group notice to leave today.
A Horsham District Council spokeswoman said: “[The caravans] gained access to Horsham Park, near the skate park.
“Sussex Police are patrolling the area and West Sussex County Council are today (August 12) serving them notice to leave.”