Louis Barretta is one of several defendants to plead before the scheduled trial next week of alleged acting boss Joseph Ligambi.
Ligambi and seven others go on trial Oct. 9.
The case focuses on gambling and loan sharking in La Cosa Nostra, and has little of the gun violence associated with previous Philadelphia mob cases.
However, prosecutors say some defendants are heard on wiretaps threatening violence as they collect loans and gambling debts.
The case covers a span of more than a decade.
Defense lawyer Brian McMonagle says Barretta's plea does not call for him to cooperate with the government at Ligambi's trial.