Slough council has issued a warning to residents after six "substantial" trees were felled in Upton Court Park.
The authority said a chainsaw had been used and the damage was not caused by "some kids mucking about".
Police should be called if anyone is seen felling trees in the park, a council spokesperson said.
The spokesperson added it was possible the bogus tree surgeon looked like a council official and may be wearing a high-visibility jacket.
The first tree was cut down six months ago and the council said it initially believed the felling was a "one-off".
However, the council's parks team has now found stacks of logs in the area and believe the person responsible is cutting the trees down so they can sell on the wood.
Councillor Joginder Bal, the authority's cabinet member for environment, said: "These are not broken saplings, it would take a chainsaw to do the immense damage we have seen.
"Our trees are precious and the only time we would fell a tree would be if it was dead, diseased or dangerous.
"Don't approach the person, but please call the police right away and report it."
A "mystery person" is believed to be posing as a local authority tree surgeon to cut down a town's mature oaks and willows, a council has said.