Derbyshire 179 for 7 (Madsen 66, Wahab 42, Thompson 3-23) beat Yorkshire 102 (Hughes 3-12, Ferguson 3-21, Viljoen 3-32)
Wayne Madsen's brilliant 66 off 28 balls led Derbyshire to a winning total of 179 for 7 as they completed a quick-fire double over Yorkshire with a rain-affected win at Emerald Headingley.
The Falcons beat the Vikings, by 77 runs, for the second time in three days after Saturday's North Group victory at Chesterfield when they scored 42 off the last three overs.
Here, after an hour's rain delay reduced the game to 17 overs per side, the visitors stormed to a 180 target and defended it comfortably to win for the fourth time in eight matches this campaign having lost their first four.
Madsen hit 10 fours and two sixes in an innings which mixed power with innovation, highlighted by his two sixes off Azeem Rafiq's offspin.
His first was smashed high over long-on into the top tier of the new North/South Stand at the Football End of Headingley before his second was reverse swept over wide third-man.
New Zealand fast bowler Lockie Ferguson then claimed 3 for 21 and medium pacer Alex Hughes 3 for 12 from their three overs as the Vikings slipped to 102 all out, losing their last six wickets for 11 runs.
Derbyshire lost Billy Godleman to the first ball of the match, bowled having a swipe at David Willey. But Calum MacLeod and pinch-hitting Pakistan quick Wahab Riaz got the innings moving, with the latter playing the lead role in a belligerent 42 off 30 balls.
They shared 66 in 6.4 overs before MacLeod holed out to deep mid-wicket to hand seam bowling all-rounder Jordan Thompson his first of three wicket on home debut.
Madsen built on that momentum in exhilarating style, reaching 50 off 22 balls before Wahab fell in similar fashion to MacLeod off Rafiq as the score fell to 114 for 3 in the 12th.
Madsen continued his onslaught before the Falcons lost 4 for 30 in the last four overs, including Hardus Viljoen and Madsen caught off Thompson in the 14th over.
Adam Lyth and Tom Kohler-Cadmore both hit sixes in the first two overs of Yorkshire's chase, the latter smashing Ravi Rampaul over midwicket and clearing the West Stand.
Both fell to Ferguson to further strengthen Derbyshire's hand at 37 for 2 in the fifth - Kohler-Cadmore caught behind and Lyth at deep square-leg.
Hughes had Kane Williamson caught low down at cover in the next over - 42 for 3 - and from there it was always going to be an uphill task for Yorkshire, who face Leicestershire here tomorrow as they search for their fifth win in nine.
Ferguson later had Gary Ballance caught at short fine-leg scooping before Hughes claimed two of those last six wickets. He had Tim Bresnan caught behind and Thompson bowled in the 13th.
Yorkshire's fourth defeat also handed Derbyshire the Blast double for the second year running, and it is the first time the county having beaten them in four straight games in any format.
This was only the Vikings third home defeat since the start of 2016.