14-year-old Prakash Naik was grazing cattle in Sushilnagar in Sandur taluk yesterday when the leopard tried to attack the herd.
When the boy tried to chase it away, the leopard pounced on him and mauled his face, police said.
Two youths who witnessed the incident ran to safety.
After the incident, enraged villagers reportedly manhandled the Forest Department staff for not taking steps to trap the animal and blockaded roads in protest, affecting traffic movement on the Hosapete-Sandur road, they said.