Police detained 14 people on suspicion of criminal property damage at the German capital's most iconic sight on Sunday after part of it was sprayed orange and yellow by environmental activists.
Last Generation said fire extinguishers were used to spray the landmark on Sunday morning.
Police said they prevented demonstrators from climbing the monument after officers noticed a hydraulic lift near the Berlin landmark.
Last Generation members have called for renewed protests in the German capital for an indefinite period.
Group calls for faster end to fossil fuel use
The group is demanding the end of fossil fuel use by 2030.
"We will not stop our protest unless a pivot is initiated," the group said. "We have to exit oil, natural gas and coal by 2030 at the latest."
The German government is targeting 2045 for a climate-neutral economy but has missed its climate protection targets for the last two years.
Berlin Mayor Kai Wegner condemned Sunday's protest, saying the city supports "freedom of expression and fair debate about our future," then adding that "with these actions, this group is not only damaging the historic Brandenburg Gate, but also our free discourse on the important issues of our time and future."
What is the Last Generation?
Since the spring of 2022, Last Generation has been protesting across Germany. Political party headquarters have been targeted with paint, as have luxury shops and a private jet at the capital's airport.
The Last Generation has made headlines in Germany for members who glued themselves to roads and airport tarmacs to disrupt road and air traffic.
Their action has triggered a law-enforcement crackdown by Germany's federal states.
The group's new protest initiative for Berlin kicked off last Wednesday with a march involving several hundred participants.