Mir hosts the popular Capital Talk show on Geo TV, which said that gunmen fired at him with automatic weapons.
He suffered three gunshot wounds and was being treated in hospital. This was the second attempt on his life.
In 2012, a bomb was recovered from his car.
Mir is seen as a critic of Pakistan's powerful security institutions, including the army and the Inter-Services Intelligence (ISI) spy agency.
Geo TV reported that Mir had informed the government and close friends that ISI and its chief would be responsible for any attempt on his life.
Global media watchdog group Reporters Without Borders said in its annual report released in February that Pakistan is one of the world's most dangerous places for journalists.
In March, Raza Rumi, of the private Express TV, was targeted in the eastern city of Lahore.
The journalist, who frequently criticises the Taliban, survived but his driver was killed and a security guard was wounded.