Castlemaine's Senior Constable Rod Webster said the Mostyn Street memorial was marked with black spray paint sometime between 2pm on Saturday and 9.30am on Sunday. 

Senior Constable Webster said the graffiti attack was "very disappointing". 

"The community deserves better and it's disappointing they have targeted the war memorial," he said. 

"We have had locals come in to say they are disappointed."

The memorial pays tribute to soldiers who served during WWI, WWII, the Vietnam War and peacekeepers in Iraq and Afghanistan and is located at the front of the RSL. 

Castlemaine RSL president Ern Plumridge said the vandals had a lack of respect for other people's property.

He said he hoped the offenders were caught and his actions punished.  

"It's a disgrace," he said. 

"I hope they catch the person who did it.

"It's a senseless act."

Senior Constable Webster said graffiti vandalism was uncommon in the area.

He said he did not believe the graffiti would be difficult to remove.  

Anyone who may have witnessed the incident should contact Senior Constable Webster on 5472 2099.