The 18-year-old tourist was taking selfies with friends at Cape Solander, south of Sydney, when he lost his balance on slippery rocks, it is believed.
He plunged 10 metres (32.8ft) into the sea below, police said.
The unnamed teen was visiting the site with 15 others and is from the UK, Sydney’s Daily Telegraph reported.
He is the second person to fall and die from the cliff in the last six weeks.
A rescue helicopter arrived around seven minutes after his friends called the emergency services.
Marine area command officers pulled the unconscious teen from the water after 30 minutes.
A helicopter flew him to land as paramedics desperately tried to revive him – but was later pronounced dead.
It is believed the group climbed down from an official viewing platform to a rock ledge above the water.
New South Wales Police Chief Inspector Chris Hill told the Sydney Morning Herald that the boy’s death appeared to be an accident.
“He was here with a group of friends to go whale watching,” he said.
“They’ve made their way down onto the rock platform. At this stage it appears to be misadventure where he’s slipped and fallen over the edge.”
The Foreign and Commonwealth Office could not confirm if the boy was British at this stage.
Police are in the process of informing the boy’s family, a police spokesman told the Daily Telegraph.
Another man fell to his death while taking photos in the same area in early June.
Cape Solander, which is 25 miles south of Sydney, is the “perfect vantage point for whale watching,” according to the national parks website.
“If you’re lucky you won’t even need to look far – whales have been known to swim as close as 200m from the coast,” the website states.
The teenager’s death also comes a few weeks after a British woman, Louise Benson, and her Australian partner fell to their deaths while taking a selfie in Portugal.
Ms Benson and Michael Kearns died on the Praia dos Pescadores near Ericeira on the country’s west coast.