DeLay also was slapped with a five-year prison term for his money laundering conviction, but Texas State District Judge Pat Priest converted that sentence to 10 years' probation, the Austin American-Statesmen said.
"This will not stand," DeLay's attorney, Dick DeGuerin, said.
Before the sentence was announced, Delay said, "I fought the fight. I ran the race. I kept the faith."
Priest said he agreed with the jury's guilty verdict.
The three-year sentence was on the charge of conspiring to launder corporate money into political donations during the 2002 elections.
DeLay, 63, is expected to appeal his conviction, handed down by the jury in November.
DeLay, a Republican, was indicted in 2005 on charges he illegally channeled $190,000 in corporate money through the Republican National Committee to help elect GOP candidates in Texas. DeLay has said the case was motivated by politics.