The structure appeared well-made and officials believe they have identified the local homeless man who built it.
That man may face charges for building the structure in a public park.
"A considerable amount of work and materials went into this," Orange County Sheriff's Department Sgt. Rich Himmel told the Orange County Register. "We are investigating this. It's a crime of vandalism. Someone has to be held accountable."
The treehouse was discovered around 8 a.m. Wednesday by a city crew pruning trees in Lantern Bay Park. When they looked up at a 50-foot Aleppo pine, they discovered the multi-layered treehouse made out of plywood.
The treehouse and the man's belongings were removed from the pine and about a dozen fish found in an aquarium were brought to a local animal shelter.
The crew also pruned the tree as planned and had to remove several limbs that were damaged by the structure.