Ikramullah Gandapur was killed after his convoy was attacked in the town's Kulachi area on Sunday, police said.
"Saddened to learn that Ikram Gandapur succumbed to his injuries," tweeted party chief Imran Khan. "My prayers go to his family. May Allah give them the strength to bear this loss."
Dera Ismail Khan, located adjacent to the South Waziristan district, which was once a stronghold of the Tehreek-e-Taliban Pakistan (TTP), has seen several such attacks in recent years.
On Sunday, the TTP claimed responsibility for the attack.
"Ikram Gandapur was wanted for having been responsible for the killing of tens of Taliban members," alleged Muhammad Khurasani, a TTP spokesperson, in a statement released to the media.
The attack in Dera Ismail Khan was the latest to target candidates or campaign workers.
In the three weeks leading to the vote, at least 179 people have been killed in attacks across the country, but mainly focused on the western Balochistan and Khyber Pakhtunkhwa provinces.
On July 11, a candidate from the PTI's rival Awami National Party (ANP) in Khyber Pakhtunkhwa was killed in a suicide attack, alongside 19 others, after an explosion at a rally in Peshawar.
Two days later, a suicide bomber targeted a political rally in the southwestern town of Mastung, killing more than 154 people, police and hospital officials said. That attack was the second deadliest in Pakistan's history.
More than 800,000 security personnel - including more than 370,000 army soldiers - will be deployed for security on election day, Pakistan's Election Commission said this week.
More than 106 million voters will vote for 272 seats in the country's lower house of parliament, as well as for the country's four provincial assemblies.
