Warning: This article contains images of dead animals.
The latest culling comes less than two weeks after 1,428 Atlantic Whitesided dolphins were killed during the islands' annual grindadráp hunt, according to Sea Shepherd.
On Wednesday night, a further 52 pilot whales were killed off the Faeroese island of Streymoy, said the charity, which shared images of the dead mammals.
It is understood initial plans involved only tagging the dolphins as part of a scientific research programme, before releasing them back into the wild.
But the local Natural History Museum said it did not have enough scientists to mark the mammals and instead the whalers slaughtered them.
Sea Shepherd believes the large size of the pod may have "influenced the decision" to cull the animals, as scientists usually only tag small pods.
A Sea Shepherd spokesperson told ITV News: "Unbelievably [they] have killed 52 pilot whales just 10 days after the horrific slaughter of 1,428 Atlantic Whitesided Dolphins.
"This brings the total pilot whales killed this year to 667.
"There is no quota for these hunts and no season so they can continue without impunity.
"This may not be the last hunt of the year despite there being no need for this meat."
It comes just a week after the Faeroese government vowed to launch a review into the way hunts are carried out amid international outcry over distressing footage showing dolphins being slaughtered.
The extent of the last cull was so large - much higher than in previous years - that it appears participants may not have been able to follow regulations to minimise the suffering of the animals.
Premier Bardur a Steig Nielsen said in a statement a week ago that his government takes this "matter very seriously".
"Although these hunts are considered sustainable, we will be looking closely at the dolphin hunts, and what part they should play in Faeroese society," he added.
Grindadráp is a local tradition regulated by law that has been practised for hundreds of years on the Faroe Islands - an archipelago between Iceland and the UK.
The hunt usually sees islanders in boats herd whales into a shallow bay where they are stabbed to death for their meat and blubber.
According to Russell Fielding, a US academic who studies grindadráp, the tradition "has provided meat and blubber for human consumption since at least the late 16th century" and is viewed by many as a key part of Faroese culture.