Dorset County Council said the rock fall on East Beach near West Bay appears to have happened in the early hours of Friday.
It follows other landslips earlier in the year caused by winter storms.
The Jurassic Coast World Heritage team urged visitors to pay heed to warning signs and avoid "putting yourself or others at risk" by venturing close to the bottom of cliffs.
Drone pictures taken by local photographer James Loveridge show debris from the sandstone cliff spread out on the beach below.
Sam Scriven, earth science manager for the Jurassic Coast World Heritage team, said the cliffs were being monitored.
"As ever, keep your wits about you, whether you are out walking, fossil hunting, having a picnic or taking selfies.
"Always stay away from top and bottom of cliffs. Landslides and rock falls can, and do, happen anytime. Never ignore a warning sign - they are there for your safety."
Bridport Harbour also posted a warning on Facebook.
It said: "These can happen at anytime and without warning. Stay a safe distance away from the bottom of the cliffs."
A section of cliff has collapsed onto a beach on Dorset's Jurassic Coast.