A lawyer by trade, Del Nido was accused of charging the local authority in Marbella millions of euros for work that was either unnecessary or never even carried out between 1999 and 2003.
The 56-year-old was first sentenced to seven-and-a-half years for the crimes by a provincial court in Malaga back in 2011.
Sevilla confirmed on Thursday that his appeal to the Supreme Court had only been succesful in reducing that sentence by six months.
"The criminal chamber of the Supreme Court has sentenced the lawyer and president of Sevilla FC, Jose Maria del Nido, in the so-called 'fees case', relating to services rendered to the local authority in Marbella," said a statement on the club's website.
"The High Court has only reduced the sentence imposed on Del Nido by the Provincial Court in Malaga that ruled on the subject in 2011 by half a year."
Del Nido has been in charge of the Andalusian club since 2002 and oversaw one of the most successful spells in its history as it won back-to-back UEFA Cups in 2006 and 2007.
Sevilla did not comment any further regarding Del Nido's future, but Spanish media reported that he will not step down to concentrate on his legal battle.