Leicestershire managed just 172 all out, with young leg-spinner Matt Parkinson taking four for 30, and the visitors passed their target in just 25.5 overs to record their second win in North Group.
Lancashire captain Liam Livingstone smashed seven sixes in racing to 90 off just 56 balls, with Hassem Hameed hitting 55 from 70 deliveries in an unbroken partnership of 133 as the visitors cruised to victory at Oakham School.
Bowling first after winning the toss proved a wise decision by Livingstone on a cloudy morning in Rutland.
There was something in the pitch for the seamers, as Joe Mennie produced an almost unplayable delivery to Cameron Delport which pitched on leg stump and moved away to hit off.
Paul Horton, a former Lancashire captain, did not last much longer as Graham Onions found the outside edge and Livingstone took the catch at second slip.
Ned Eckersley and Mark Cosgrove began to rebuild the innings, but when their third-wicket partnership had reached 42 Eckersley attempted to reverse sweep the left-arm spin of Stephen Parry and top-edged high to Alex Davies coming in off the boundary at backward point.
Colin Ackermann struggled from the start against Parkinson and was quickly bowled by a googly he completely failed to pick, before Neil Dexter, who had yet to get off the mark, tried to loft Parkinson over mid-off and failed to clear Josh Bohannon.
Cosgrove was Leicestershire's only real hope of posting a competitive score, but the Australian had only just passed 50 when he played and missed at Parkinson, dragged his rear foot and Dane Vilas completed a smart stumping.
Tom Wells lofted Parkinson high to Parry at long-on, Ateeq Javid steered Parry tamely to Livingstone at wide extra cover, and Dieter Klein was lbw to Onions as the Foxes were bowled out with an over unused.
Davies and Hameed gave Lancashire a solid start to their reply, and though Davies top-edged a pull at Klein to be caught behind for 23, Livingstone ensured the chase would end very quickly.
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