According to anti-persecution charity Release International, Mukhtar Masih, 70, is accused of pinning a blasphemous letter to the door of a mosque in Gujanwala, Punjab.
The letter made derogatory remarks about the Koran and Muhammad.
Blasphemy is a crime punishable by death in Pakistan.
Pakistan
Population: 196.7 million (3.9 million Christians)
Main Religion: Islam
Government: Islamic republic
Open Doors World Watch List Rank: 4
Source of Persecution: Islamic extremism
An estimated 700 Christian women and girls are abducted every year in Pakistan
The Easter 2016 bombing in Lahore by the Taliban was aimed at Christians, and killed at least 69 people
Initially, Masih's entire family was detained - including his three grandchildren. All but Mr Masih were later released and have gone into hiding.
Mr Masih is still incarcerated.
Locals believe that the accusation is an attempt to seize his land.
Pakistan ranks as the fourth worst country in the world when it comes to the persecution of Christians, according Open Doors.