The attack happened sometime around 11 a.m. at Azzie's Container Yard at 314 W. Beach St., animal services interim general manager Lynn Miller said.
A 58-year-old man who was there for business purposes was attacked by a pit bull named Princess when he stepped onto a sidewalk to avoid an oncoming truck, Miller said.
The man was taken to Watsonville Community Hospital with puncture wounds to his left calf.
Animal services officers responded and took custody of the dog, which was euthanized with its owner's permission, Miller said.
He said the dog was used for nighttime security at the business and that there are "Beware of Dog" signs posted in the area. The dog had recently been quarantined for biting someone in early September, Miller said.