Admitted to the hospital since late last month due to respiratory problems, his son, Test player, Shoaib Mohammad said his father's condition had deteriorated since yesterday.
"He is now on a ventilator and in intensive care unit," Shoaib said.
"He is facing respiratory complications due to his lung cancer," he said.
Hanif, 81, known as the little master for his batting skills was diagnosed with lung cancer in 2013 and went to London for surgery and treatment and returned home well.
Hanif was a member of Pakistan's first touring Test squad that went to India in 1954-55 and went on to play 55 Tests scoring a memorable 337 runs against the West Indies in 1957-58.
It remains the longest innings in Test history (and stood as the longest in all first-class cricket for over 40 years).