The Pakistan Air Force (PAF) said that the French-made jet went down near Dera Ismail Khan town.
Two people were killed in the crash, officials said.
"Pakistan Air Force reports with regret that a PAF Mirage Aircraft, while on a routine operational training mission, crashed," PAF said in a statement.
A search and rescue operation is underway, while a board of inquiry has been ordered by Air Headquarters to determine the cause of accident.
The immediate cause of the crash was not known but it appeared to be due to some technical fault. There were no news on any of the pilots.