The man, whose name has not been released, shot himself at the home the Grease star owns with her husband, John Easterling.
Local police from Jupiter Inlet Colony were called around 12:15 p.m. However, Newton-John and Easterling were not at the house on Monday.
Although the death appears to be a suicide, police are reportedly treating it as a death investigation led by the Jupiter police. Contractors were doing work at the residence and one contractor was seen crying Monday afternoon.
The home is reportedly being sold for $5.6 million.
Newton-John lost her sister, Rona, in May after she battled a brain tumor.