Alleva confirmed the length of the deal after he and Miles's agent, George Bass reached an agreement on Wednesday afternoon.
Alleva says financial details of the contract are still in the negotiation process and will be announced at a later date.
Miles' previous contract paid about $3.75 million annually through 2017. He has not received a raise since 2008, though he has since received an extension and raises for assistants.
Miles is 85-20 at LSU since arriving in 2005, with one national title in the 2007 season and two BCS championship appearances. LSU's victory over Arkansas last Friday clinched Miles' fifth 10-win season with the Tigers.