Leicestershire 178 for 7 (Ackermann 62*, Lamb 3-30) beat Lancashire173 for 9 (Livingstone 48, McKay 3-29) by three wickets
Three-time champions Leicestershire got their latest NatWest T20 Blast campaign off to a flyer by beating Lancashire at Liverpool, chasing down 174 off the last ball.
The Foxes have not qualified out of the North Group since their last success in 2011.
But they will be more confident of doing so this year having upset Lancashire by three wickets as Colin Ackermann led the way with a measured 62 not out off 41 balls.
The South African even hit the last ball of the match for six with two needed.
The Lightning, who won their opener at Durham on Friday, posted 173 for 9, having been invited to bat, with Liam Livingstone hitting 48 off 33 balls and Jos Buttler 39 off 21.
They shared 72 in 6.1 overs for the fourth wicket, but visiting captain Clint McKay impressed with 3 for 29 as Lancashire struggled in the second half of their innings.
Lancashire lost three wickets in the power play, including McKay getting Arron Lilley and Steven Croft in the space of two balls in the fifth to leave the score 40 for three.
Pinch-hitter Lilley had hit 30 off 17 balls from number three, but Livingstone and Buttler shared 72 in 6.1 overs for the fourth wicket, both hitting two sixes, to really get things going on a glorious Merseyside day.
Buttler hit his third ball over long-on off former Red Rose Academy graduate Callum Parkinson, the left-arm spinning twin of Lancashire's Matt.
Parkinson then got both Buttler and Livingstone, caught at long-off and stumped respectively, to spark the Foxes fightback.
All-rounder Danny Lamb pulled Gavin Griffiths for six in the 17th over, but that was the only boundary from midway through the 13th as Lancashire fell from 112 for 3.
McKay, an expert when it comes to change of pace, only conceded five off the last over as the Lightning tail failed to regain earlier momentum.
The Foxes chase got off to the perfect start as Luke Ronchi lofted the first ball from off-spinner Lilley for a straight six, and he shared 42 inside four overs for the first wicket with Cameron Delport.
But the pair fell in the space of three balls at the end of the fourth and start of the fifth. Delport drove Lamb (three for 30) to mid-on for 19 and Ronchi was caught at cover for 17 off left-arm spinner Stephen Parry's first ball as the score fell to 42 for two.
Mark Cosgrove, however, hoisted Parry for six at the start of the ninth over as he and Ackermann settled quickly and put the Lightning back under pressure with a 61-run stand. They helped reach halfway at 99 for two.
Not even the loss of Cosgrove for 34 off 21 - caught at wide long-on off Lamb - Ned Eckersley and Lewis Hill could derail the Foxes, who fell to 128 for five in the 15th.
With Ackermann still there on 38, they needed 43 off 30 balls. The contest became much closer than expected with some tight bowling at the death, and the visitors made hard work of six needed off the last from Kyle Jarvis.
Mat Pilans was run out off the penultimate ball, leaving two needed. But Ackermann hit the last over cover for his second six to clinch a win which had always looked likely throughout the chase.
Lancashire's captain Steven Croft confirmed that overseas all-rounder Ryan McLaren missed the game with a tight hip flexor, while fellow overseas bowler Junaid Khan should arrive from Pakistan in time for Friday's Roses clash following visa issues.