The Wanganui District Council building was vandalised overnight, with the "W" being replaced on a council sign with a "Wh".
The council voted last week not to include the letter "h" in the official spelling of the city's name.
The home of Mayor Michael Laws was targeted last Thursday night when a rock was thrown through his daughter's bedroom window.
The council says the original sign, with its original spelling, has been restored.
