The blast occurred when an improvised explosive device (IED) went off in Bajaur agency, bordering Afghanistan, officials said.
The deceased was a member of the Nawagai Aman committee, which has been targeted by militants in the past.
Jamatul Ahrar faction of the banned Tehreek-i-Taliban Pakistan (TTP) claimed responsibility for the blast.
Bajaur is one of seven districts in Pakistan's semi-autonomous tribal belt, where Taliban militants are believed to have carved out strongholds.
Polio workers, peace committee members have been targeted in the tribal region in the past few years by militants.