Locals discovered the monkeys in a forest clearing and were initially baffled by the apparent mass death.
Suspecting the mammals had been poisoned, postmortems were carried out which revealed they all had heart attacks at the same time.
Vets in the Kotwali Mohammadi area of the northern Indian state of Uttar Pradesh carried out investigations and concluded they were scared to death by a tiger.
Vet Dr Sanjeev Kumar said: ‘It was confirmed in the post-mortem report that the monkeys died due to cardiac arrest.
‘They could have died due to tiger’s roar as tigers often traverse that area.’
Forest department workers found the monkeys on Monday and an upsetting video shows them stuffing the bodies in polythene bags.
Villagers reported tigers are often in the area and were heard roaring at the time of the deaths.