Khyber Pakhtukhwa's Minister for Law and Parliamentary Affairs Israrullah Khan Gandapur was greeting people at his Dera Ismail Khan home on the occasion of Eid-ul-Azha when the attack took place, police said.
Police said at least 20 people were also injured in the bombing. They said about 500 people were present when the bomber blew himself up.
According to initial reports, the suicide bomber entered the home of Gandapur in Kulachi area of Dera Ismail Khan after killing two guards.
The security forces rushed to the blast site and cordoned off the area.
The injured were shifted to a nearby hospital.
Gandapur was elected as an independent candidate during the 2013 general elections and later joined the Pakistan Tehreek-e-Insaf led by cricketer-turned-politician Imran Khan.