It was around 11:10 a.m. when paramedics and rescue crews were called out to the zoo, located on the 3400 Girard Avenue.
Police say the 57-year-old man was working under a 9-foot long heavy duty golf cart when it fell off the jack and onto his chest.
No one was around when it happened. The worker lay pinned underneath the vehicle for an undetermined amount of time before he was discovered after failing to respond to his radio.
The worker was transported by ambulance to the Hospital of the University of Pennsylvania where he died.
Chopper 6 HD was overhead when police were on the scene investigating in the maintenance area at the back of the zoo.
In a statement released by the zoo, officials say the longtime employee was performing his duties when the tragic accident occurred.
The worker's name has not been released. However, a zoo spokesperson said the mechanic was well known and well liked.
Authorities are investigating.