Jack the cat is possessive about his territory, his owners say
The unwelcome intruder was forced up a tree - twice - by the family pet, a tabby cat called Jack.
The terrified bear was only able to make its escape when owner Donna Dickey called the hissing cat into the house.
Ms Dickey said Jack liked to keep a close watch on his territory and often chased away small animals, but one of this size was a first.
"We used to joke, 'Jack's on duty', never knowing he'd go after a bear," Donna Dickey told local newspaper The Star-Ledger.
"He doesn't want anybody in his yard," she added.
The bear was first spotted in the tree by neighbours who thought the 15lb (7kg) cat was just looking up at it.
They then realised the bear was afraid of the cat.
After some 15 minutes, the bear descended, but was chased up another tree, before finally making its escape when Jack was called indoors.
Bear sightings are not unusual in the area of West Milford in New Jersey, which experts say is one of the state's most bear-populated areas.