Farida Afridi, who worked for the NGO Sawaira, was on her way to work when the motorcycle-borne gunmen fired at her in Jamrud sub-district of Khyber tribal agency.
She was killed instantly, the officials of the local political administration said.
Sawaira is based in Hayatabad area of Peshawar, the capital of Khyber-Pakhtunkhwa province, and works for the rights of women.
No group claimed responsibility for the attack.
The Taliban and Islamic clerics have threatened NGOs in several parts of northwest Pakistan and the tribal belt bordering Afghanistan.
