Sports ministry spokesman Faik Ali said the 30-year-old Zahoor was given the suspension after appearing before a three-member committee of the national anti-doping body on Monday.
Committee member Khalid Mehmood said Zahoor could appeal against the ban.
Zahoor competed in the 2004 Athens Olympics, but failed to get out of her heat in the 1,500 meters.
Pakistan will not compete in any of the track and field event at next month’s Commonwealth Games in New Delhi.