Geelani was arrested by police at New Airport Road outside his Humhama residence, a Hurriyat spokesman said.
He said the separatist leader, whom the police had kept under house arrest, was then taken to Police Station Humhama.
The separatists had called for a march to Anantnag district, which has seen highest number of deaths in the ongoing unrest in the Valley.
Geelani tried to march towards Anantnag and participate in a rally to be held at Lal Chowk there to express solidarity with people, the spokesman said.