Eyewitnesses said the attacker shouted “this is for Syria”.
The man, who has not been named, was allegedly seen clutching a knife in his hands as officers keep him away from commuters.
Scotland Yard declared they were treating the attack, which happened at Leytonstone tube as “a terrorist incident”.
The incident began at 7.06 pm with reports of a stabbing. It is believed the assailant then went through the exit gate and there he threatened other people with a knife.
Officers tasered the man at the scene and took to an east London hospital, where he is in police custody.