The defense had argued that Selleck didn't check the veterinarian records of the 10-year-old Zorro.
The bulk of the San Diego County jury's award is for the price of the horse. The rest is to cover boarding costs. A second trial next week will determine how much Selleck should be paid in punitive damages.
Selleck is best known for his role on TV's "Magnum, P.I." in the 1980s.