Berlusconi "was the mind behind the mechanism" that allowed his Mediaset business empire to dodge taxes, they said in a written explanation of their decision to turn down Berlusconi's final appeal on August 1st.
They also said the theory that Berlusconi was in fact a victim of the fraud was "absolutely improbable".
"The players were a restricted circle which was not at all on the sidelines of the group but was so close that they all personally frequented the owner, the defendant Berlusconi," the judges said.
"This defendant, this businessman would have had to have been completely clueless" not to realize the tax fraud scheme that was in place, they said.
Berlusconi faces possible expulsion from parliament over the verdict and a court in October is expected to decide whether he will have to serve his one-year sentence as community service or under house arrest.
Berlusconi was found guilty of artificially inflating the prices paid for film distribution rights when they were sold to Mediaset in order to reduce tax payments.
The August 1st ruling has sent shockwaves through Italy's political establishment, with supporters of Berlusconi threatening to pull out of the government if plans to eject him from parliament go ahead.