The 31-year-old was pulled over by police in London back in May while driving his Mercedes Benz on the A406 North Circular, the BBCreports.
His windows were tested with specialist equipment for light penetration and were ruled to be below the legal limit.
On Monday, the striker pleaded guilty to driving a car in a dangerous condition at Wimbledon Magistrates’ Court and was handed fines totalling £865.
That was made up of a £650 fine, a further £150 in costs and a £65 surcharge.
The court heard that the police officer who made the arrest classed the windows as “dangerous for pedestrians” and Deeney was instructed not to drive at night time.
Deeney had bought the vehicle with the windows already tinted and he’s since made the necessary changes for it to comply with the law.
The Hornets skipper attended court, but left before his case was heard. His lawyer said that he needed to go for medical treatment.
Deeney is currently sidelined with a knee injury after undergoing an operation towards the end of August.
He played every minute of Watford’s opening two Premier League games before going under the knife, but his side have toiled in his absence.
Manager Javi Gracia was sacked and replaced with Quique Sanchez Flores in September, but the Vicarage Road outfit remain winless in the league after eight rounds of action.
Watford prop up the table on three points and suffered a humiliating 8-0 drubbing at the hands of champions Manchester City at the Etihad last month.
Deeney, who scored 11 goals in all competitions for the Hornets last season, is expected to return to the pitch later this month.
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