They had been suspected of links to the lynching and burning alive of Shahzad Masih and Shama Shahzad in Punjab province in November 2014.
Masih and Shahzad, who were 26 and 24 at the time of their deaths, were targeted by a mob in the town of Kot Radha Kishan following accusations they disrespected Islam by tearing pages out from a Quran.
The couple was thrown into an industrial kiln in an attack which demonstrated how an allegation of blasphemy - true or false - has sometimes prompted vicious violence in Pakistan.
An anti-terrorism court in Lahore sentenced five men in November 2016 to death over the murders of Masih and Shahzad - who was four months pregnant.
Eight other men who were part of a group involved in the attack were jailed for two years.
According to Associated Press, the 20 people acquitted by a Pakistani court on Saturday were indicted in the case at a later stage.
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