Kruger shook his head after the sentence was imposed Thursday by federal Judge Jed Rakoff.
The chair of the powerful Senate Finance Committee from 2008 to 2010 admitted that he accepted nearly a half-million dollars in bribes from a variety of business people.
The 62-year-old Brooklyn resident had faced a minimum of nine years in prison but the judge gave him credit for extraordinary good deeds.
Earlier this year, he resigned from the state Senate seat he has held since 1994.
Kruger, a Democrat, was the powerful Senate Finance Committee chairman from 2008 to 2010, when Democrats controlled the Senate.