Lancashire end Derbyshire's winning start to T20 campaign
The Falcons had won their first two North Group matches, but were beaten on the same pitch used for Friday’s Roses tie, hence why 22 overs of spin were bowled.
Derbyshire posted 152/8 having elected to bat, and Buttler came in at 56/3 in the seventh over of the chase.
Lancashire’s second win from four was secured with five wickets in hand and nine balls to spare.
Wayne Madsen top-scored with an inventive 35-ball 52 for the Falcons, while Lancastrian Matt Critchley opened and hit 40 and ex-Red Rose all-rounder Luis Reece added 38.
But the visitors lost six wickets and scored only 41 runs in the last six overs of their innings.
Leg-spinner Matt Parkinson claimed three for 17 on his limited overs debut, while Pakistan seamer Junaid Khan added three for 28.
Reece shared 60 in 7.1 overs for the second wicket with Critchley and 45 in 5.1 for the third with Madsen as the visitors reached 111 for two after 14.
Lancashire captain Steven Croft employed only two overs of seam in the first eleven.
And while the first half of the innings may not have gone quite to plan for Croft, the second half certainly did.
Both sides used eight bowlers, with 16 a new English record for a T20.
Having earlier struck with his sixth ball to get Critchley caught at deep mid-wicket in the ninth over, Parkinson had Reece caught at long-off in the 15th and bowled Matt Henry in the 17th.
Madsen reached 50 in the last over before edging behind a slower ball bouncer from Junaid, who yorked Alex Hughes next ball and had a huge lbw shout against Daryn Smit turned down on hat-trick ball - the last of the innings.
Madsen hit six fours and a straight six.
Lancashire’s chase was boosted at the end of the third over when Karl Brown offered a sharp low chance to debutant Hamidullah Qadri at square-leg off Hughes on 15.
Liam Livingstone (23) then hit sixes over long-on and straight off overseas duo Henry and Imran Tahir in the fourth and fifth overs to take the score to 48.
But Derbyshire hit back as Livingstone, later in the fifth over, was the first of four wickets to fall for 24 as the score slipped to 72 for four in the ninth.
Livingstone holed out to long-on to Tahir, who later trapped Croft lbw.
Sandwiched in between, reverse sweeping Arron Lilley fell for a golden duck as Critchley took a stunning diving catch at backward point off Reece’s left-arm spinners - he usually bowls seamers.
And Brown holed out to long-on off Hughes for 30.
Lancashire reached halfway at 85 for four with Buttler and Dane Vilas together and were still ahead on Duckworth Lewis Stern courtesy of their healthy start.
Buttler took few risks and ran particularly well as he and Vilas took the target below 50 in the 12th over.
When Hardus Viljoen had Vilas caught at fine-leg hooking for 20, Lancashire were 112 for five in the 14th.
The hosts went 7.3 overs without a boundary from midway through the tenth to the end of the 17th, by which stage they were 135 for five and needing 18 more.
Buttler was unbeaten on 36 and hit only three fours in his match-clinching innings. Ryan McLaren (24 not out) hit the winning runs.