Council roading manager Michael Voss said the decoration had lights built into it.
''The tree-shaped decoration was located on a street lighting pole above Regent Florist and Paper Plus and someone has gone to quite a bit of effort to remove it. Although it might have been seen as a harmless prank, these decorations are costly to replace.''
The Oamaru Christmas decorations were bought about 10 years ago with money raised by the community, and they remained a valuable community asset enjoyed by everyone, he said.
There would be a short amnesty to allow those responsible for its removal to return the decoration, Mr Voss said.