Overnight, some garden beds and fencing at the Eltham North Adventure Playground carpark were destroyed.
Nillumbik Council is working closely with police in an effort to catch those involved.
Mayor Karen Egan said every effort would be made to catch those behind this heartless act.
“The garden beds were planted by children from the local [Eltham North] school and there has been great excitement as we approach the completion of this project.
“The destruction is a small setback for a project that has seen the community and the Council working together.
“While this is extremely disappointing we will not let this distract from the hard work and dedication put in by so many to ensure our [Eltham North] great playground can once again be enjoyed by our community,” Egan said.
The Eltham North Adventure Playground was destroyed by fire in December 2017 and Nillumbik Shire still intended to complete the rebuild by Christmas 2018.