They were sentenced at Preston Crown Court for offences including conspiring to supply Class A drugs and money laundering.
Gang leader Zahid Khan, 40, carried out the drug deals and used couriers to transport heroin, cocaine and cash.
Police had seized 1kg of heroin, 1kg of cocaine and nearly Â£50,000.
Lancashire Police's Serious and Organised Crime Unit began investigating the gang in January 2015.
They found couriers were taking drugs to and from Preston, Accrington, Bolton and Leicester.
A seventh man is due to be sentenced on 26 July. Two other men were given suspended sentences and community service after pleading guilty to money laundering offences.
Det Sgt Mark Lee said: "Our investigation revealed that Khan and his associates couriered drugs around the county and beyond and laundered the proceeds of their drug deals.
"As a result of this operation, we have dismantled a significant drugs network, taking large quantities of cocaine and heroin off our streets, ensuring that those involved in the conspiracy have been brought to justice."
A proceeds of crime investigation will follow.
Six men involved in a drugs and money-laundering network across Lancashire, Greater Manchester and Leicester have been jailed.