Thunberg, 21, joined hundreds of protesters in a march against fossil fuel subsidies on Saturday. The protest turned into a stalemate as dozens of police officers, some on horseback, tried to prevent protesters from blocking the main road.
Police intervened and forced Thunberg onto a bus full of demonstrators.
The demonstration was organized to protest against the Dutch government's tax breaks for companies linked to the fossil fuel industry, including energy company Shell and airline KLM.
Several protesters broke through police lines but were quickly apprehended and handcuffed. Thunberg told AFP news agency, "It's important to demonstrate today because we have a planetary emergency. We must do everything to prevent this crisis and save human lives."
Asked if she was worried about police intervention, she said: "Why should I be worried?"
The Hague police told the BBC: "While we cannot comment on individual cases, we can confirm that the people who were picked up by police and put in vans were formally arrested for blocking the highway. Blocking the highway is against the law."
Thunberg has been a prominent climate activist since the age of 15.
