Berlusconi had argued that a Milan tribunal had acted unjustly by refusing to reschedule a fraud trial hearing in March 2010, despite his claim that he was busy with governmental business.
An appeals court in May had upheld a one year prison sentence and a five-year ban from public office for the magnate, but the case could have collapsed if the tribunal had been found guilty of preventing Berlusconi from having every opportunity to defend himself.
The trial risked being thrown out and begun again from scratch - a move which would have made it almost certain to expire in 2014 under Italy's statute of limitations without a final verdict.
The constitutional court, however, ruled that Berlusconi's excuse for being absent was not valid as he had purposely brought forward a meeting which did not have to be held at that time.
"They are trying to eliminate me from political life but I'm forging ahead," said Berlusconi, who has long held a grudge against "Communist" judges in Italy who he claims are out to persecute him.
The fraud case revolves around prices of film distribution rights bought by the media magnate's company Mediaset that were artificially inflated in order to avoid taxes.
With Berlusconi's claim rejected, it will now go to Italy's highest court of appeals later this year.
The 76-year-old is also a defendant in a trial for having sex with an underage 17-year-old prostitute while he was still prime minister, and then abusing the powers of his office by putting pressure on police to release her from custody.
A verdict in that case is expected on Monday.