The 68-year-old Fumo was convicted of defrauding the state Senate and two nonprofits of millions. Prosecutors say he used the funds to maintain his mansion, spy on rivals, and pay for yachting trips and luxuries.
They say Senior U.S. District Judge Ronald Buckwalter gave no reason for departing from federal guidelines of more than 20 years.
Defense lawyers will argue to overturn Fumo's conviction.
They say one juror referenced deliberations online and another learned the Philadelphia Democrat had been acquitted in a prior case.
The Philadelphia Democrat was perhaps the most powerful Pennsylvania lawmaker in a generation, controlling scores of jobs in and out of state government.