The Fridays for Future movement aims to demonstrate for climate protection and democracy in Germany on Friday.
With the European elections scheduled in nine days, protests are to take place in around 100 cities in Germany, the organization says.
Protests are planned in 13 other EU countries by July 7.
The movement is calling for an EU-wide phase-out of coal, oil and gas by 2035 and a doubling of investment in renewable energies and climate-neutral industries.
The new European Parliament must take a clear stance in favour of climate protection and democracy, Frieda Egeling, spokeswoman of Fridays For Future Berlin, said in a statement.
Larger demonstrations and rallies are to take place in front of the Brandenburg Gate in Berlin, as well as in Hamburg and Munich.
In Berlin, 10,000 participants have been registered. Some 15,000 protesters are expected in Hamburg and some 8,000 are expected in Munich.
Climate activists want to use the upcoming rallies to draw attention to the importance of the EU in tackling the climate crisis.
In Germany, the European elections will take place on Sunday, June 9.
