In a ruling handed down on April 11 but only made public on Thursday, the court in the northern town of Ivrea awarded the plaintiff a state-funded pension.
The ruling is subject to a possible appeal.
Roberto Romeo, 57, had testified that his work duties obliged him to use his mobile for three to four hours of each working day for 15 years.
"For the first time in the world, a court has recognised a causal link between inappropriate use of a mobile phone and a brain tumour," his lawyers, Stefano Bertone and Renato Ambrosio said in a statement.
Romeo said he did not want to demonise mobiles, "but I believe we have to be more aware about how to use them.
"I had no choice but to use my mobile to talk to colleagues and organise work - for 15 years I was calling all the time, from home, in the car.
"I started to have the feeling of my right ear being blocked all the time and the tumour was diagnosed in 2010. Happily, it was benign but I can no longer hear anything because they had to remove my acoustic nerve."
A medical expert estimated the damage to Romeo at 23 percent of his bodily function, prompting the judge to make a compensation award of 500 euros per month to be paid by INAIL, a national insurance scheme covering workplace accidents.
Scientific studies of the potential health risks of mobile phones have mostly concluded that they pose no serious risk to human health at the level of most people's use.
Heavier use may pose some risk, other studies have found, and many experts say it is too early to do a proper assessment of what is a relatively new technology.
