Visitors at Tama Zoological Park were able to witness the drama unfold as the disguised zoo keeper managed to at first evade capture before being finally subdued by a pretend tranquilliser gun.
During the escape the "snow leopard" managed to "maim" an unfortunate zoo-keeper, who was rushed off in an ambulance.
A similar simulation is conducted each year at alternating zoos across Tokyo to remind staff members what to do in the event of a real animal escape.
"We think it is very important, and it is our responsibility to carry it out with seriousness."
Previous animal costumes used as part of the drill have included zebra, rhino, lion and orangutan outfits.