The court handed John Tomic an eight-month sentence. But in line with Spanish law, he will not have to go to prison since he has no criminal record and the sentence is for less than two years.
The judge presiding over Madrid criminal court No. 8, Jacobo Vigil, found "Mr. Tomic dealt a head-butt to the face of Mr. Drouet. It was not proven that Mr. Drouet had previously assaulted Mr. Tomic."
The court also issued a restraining order of 500 metres (yards) on John Tomic that he must maintain with Drouet, Bernard's former training partner.
The decision can be appealed.
The ATP banned the elder Tomic from all events following his assault on Drouet outside a Madrid hotel on May 4.
The 20-year-old Tomic has a promising career, but it's been sprinkled with controversy.
In November, he was fined and put on a 12-month good-behaviour bond after twice being stopped by police for driving offences near his Gold Coast home.
In late October, police were called to a high-rise apartment building in the Australian resort of Surfers Paradise after residents saw two men, one of them naked, wrestling and fighting in a hot tub on the balcony. One of the men was later identified as Tomic.