An election tribunal earlier this month declared Maulana Ahmad Ludhianvi, head of a group called Ahle Sunnat Wal Jamaat (ASWJ), the elected member for the town of Jhang in Punjab province.
Ludhianvi, whose organisation is listed as a terrorist outfit by the Pakistani government, came second in the seat in the May 2013 general election to Shaikh Mohammad Akram of the Pakistan Muslim League-N (PML-N) party.
But he took the matter to an election tribunal and successfully challenged Akram over allegations of vote-rigging and defaulting on a loan.
"The bench today suspended the order of the election tribunal disqualifying Shaikh Mohammad Akram and the notification by Election Commission of Pakistan declaring Maulana Ahmad Ludhianvi a returned candidate," a court official told AFP.
The court would hear the appeal in three months time, he added.
Akram's lawyer Makhdoom Ali Khan argued that the tribunal could not declare the runner-up as victor because when a candidate was disqualified, a fresh election should be held.
The hardline Sunni Muslim ASWJ is widely seen as a front for Sipah-e-Sahaba Pakistan, a group formed in the 1980s and responsible for murdering hundreds of Shiite Muslims whom it considers heretics.
Ludhianvi ran on the ticket of the six-party religious alliance Muttahida Deeni Mahaz (United Religious Front), which did not not win a seat in the vote last year.
PML-N emerged with a majority and formed the government under Prime Minister Nawaz Sharif.
ASWJ is also known as the political arm of Lashkar-e-Jhangvi, one of the most active militant groups in Pakistan and responsible for a string of bloody attacks on Shiites.