The rare sagaie, or javelin point, was crafted by a stone age inhabitant of the caves and is the only complete example of its kind found in the UK.
It is being hailed by the tourist attraction as major find and a signal that further exciting artifacts could lie just below the surface.
Dr Paul Pettitt, director of the archaeological dig, said: "This sagaie, made of antler, most probably reindeer, functioned as a spear or javelin point.
"This form of weapon was common on the continent around the time of the late Paleolithic, the Magdalenian, and used by hunter-gatherers about 14,000 to 15,000 years ago.
"These are rare, only a handful of fragmentary samples are known from Britain. This is the only complete sagaie I know of from the UK."
The find was made on the first day of an archeological dig aiming to find evidence of Neanderthal or early human occupation at the caves.
The caves are the oldest known dwellings in the UK but there has not been a major dig at the site for more than 80 years.
Nick Powe, owner of the attraction, said: "This is a very exciting find and we are anticipating more.
"We think it was probably used to kill an animal as the tip of it is broken off.
"It is basically a sharpened reindeer antler and to find it on the first day is amazing.
"Many Torbay residents know Kents Cavern as a tourist attraction, but I don't think many realise just how important an archaeological site the caves are, not just in Britain but in Europe, and it is the oldest Scheduled Ancient Monument in Britain, with evidence of human occupation dating back half a million years — and as such it's the oldest recognisable human dwelling in the entire country."
Archaeologists also hope to learn more about the origins of Kents Cavern's use as a human shelter, and establish firm dates for the first occupation of the cave by Neanderthals and early members of our own species.
The dig will continue until September 10, and can be viewed as part of the cavern tour.
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