New York native Heather Fretes said she discovered the sexual attack in progress after her pit bull-boxer mix suddenly began barking at a walkway between two local garages, the New York Post said Sunday.
Fretes said when she investigated what was upsetting her pet, she found a white man in his 20s struggling with the girl.
Armed only with her clearly antagonized animal, Fretes said she screamed at the man until he fled into some bushes nearby.
"I yelled, 'What's going on here?' and the guy held up his pants and started running," Fretes said, "and the little girl came out crying. She told me he was trying to pull down her shorts."
With the young girl back home safe and sound, Fretes was quick to credit her dog's instincts.
"He's a big hero," she told the Post. "He saved that little girl."