The health worker, identified as Salma Farooq, was found dead in Koh-e-Daman village with torture marks on her body.
She was kidnapped from her house in Guluzai village, a suburban locality of Peshawar district.
Police said around eight armed men had entered the house of Farooq, held the family hostage at gunpoint and took the woman away with them.
Enraged family members and neighbours had protested against the kidnapping and blocked the Peshawar-Islamabad motorway near Chamkani for about an hour today.
The demonstrators had given two days time to police to recover the kidnapped health worker.
The family members had feared that Farooq was kidnapped because of her involvement in the polio campaign and that she had no enmity with anyone.