The 56-second video from surveillance cameras shows the boy riding his bike Tuesday when the dog attacks him. The cat immediately charges out and scares off the much-larger dog.
The boy suffered bite wounds, but his family says he's going to be OK. The YouTube video shows several deep bites on the boy's leg.
"My cat defends my son during a vicious dog attack and runs the dog off before he can do additional damage. Thankfully, my son is fine!" uploader Roger Triantafilo wrote with the YouTube video.