It shows a bearded "hipster" enjoying a night out in Chester, with the script reading: "Every night people are out; laughing and having fun.
"But at the end of the night, a creature emerges. It has no respect for the city and pees in dark corners. But we are fighting back!"
Cllr Karen Shore, the council's cabinet member for environment, said: "Most party-goers will enjoy the festive season and respect our beautiful city.
"However, a minority are damaging historic structures by using the city centre as a public toilet. The liquid-repelling paint has been applied in secret locations across the city.
"Anyone spending a penny in public this festive season may get more than they bargained for."
The famous walls are a two-mile sandstone circuit and represent one of Chester's most popular tourist attractions.
The Romans began building them between 70AD and 80AD as a defensive structure to protect the city and fortress.
Apart from a 100-metre section, the walls almost completely surrounded the ancient city section of Chester, with a number of 'gate' entrances.