The sign was displayed on Pleasant Grove Blvd., east of I-15.
ABC 4 has learned that the sign was placed at the scene to warn drivers of a sewage line project going on by Pleasant Grove City crews nearby.
Instead of the road construction warning, the sign read: ZOMBIE ATTACK PREPARE!
Calls to the city offices were not immediately returned.
In a similar incident in September, someone apparently hacked into an electronic road sign along I-15 in Utah County, changing the message to an anti-homosexuality message.
Stay tuned to ABC 4 News and ABC4.com for more on this story.