The incident was reported just before 3:20 p.m. in the 7400 block of Canoga Avenue, according to the Los Angeles Fire Department.
Fire officials said the tree trimmer fell 35 feet onto a 10-foot high iron fence. Before the fall, he was trimming a palm tree.
The worker was pronounced dead at the scene.
Further details were not immediately released, and it's unknown what caused the man to fall.
An LAFD urban search and rescue team responded to recover the body.
The victim's name has not been released.