Caleb Jewell and Brooke Guest scored half-centuries, but the Falcons were unable to see off Hampshire at the Utilita Bowl.
Ben Mayes put on 111 in 72 balls with James Fuller (54 off 39) to take Hampshire to their fifth win in the competition, after fifties for Fletcha Middleton and Ben Brown.
Derbyshire Falcons had been in control after posting 339 thanks to 98 for Jewell and 76 for Guest but they were eliminated from the One-Day Cup, and are still yet to win a List A match at Utilita Bowl in seven attempts.
Hampshire now know a final fixture win over Gloucestershire will see them into the knockout stage for a fourth straight season.
Mayes and Fuller had joined at 206 for five, with Derbyshire boasting a tight grip on the match.
Ali Orr and competition top-scorer Nick Gubbins had leaned into the chase with relish, finding boundaries with glee to put on 55 in the first seven overs.
But fell in quick succession to Aitchison. Gubbins ended a 257 run, across three innings, without being dismissed when he was bowled and two overs later Orr chopped on.
Middleton and Brendon McMullen straightened things back out with a flowing 66-run stand, but McMullen tamely chipping back to Joe Hawkins, drew the Falcons back to favourites.
Middleton and Brown both posted their first fifties in the One-Day Cup but neither kicked on but just as Hampshire’s hopes were fading, their wonderkid arrived at the crease.
Having scored four off his first 11 balls, he got moving with a cut boundary before a ludicrous reverse paddle found his groove.
Mayes scored a fifty on his debut against Glamorgan to stick his name in the limelight, and played off that with a masterclass of modern shot-making. His second half-century came in 39 balls.
At the other end, Fuller used brute power to clear the ropes four times in his 38-ball fifty before he was caught and bowled by Hawkins and Felix Organ was bowled.
Andrew Neal took out the jitters by middling through midwicket as the hosts took the four points with five balls to spare.
Derbyshire were given the first go on a batting paradise, and despite Kyle Abbott’s miserly opening spell, found runs flowed easily throughout.
Jewell was the sparkle in the innings as he lusciously and repeatedly drove through the covers during a 99-run stand with former Hampshire batter Harry Came.
It was just the start of a series of bulky partnerships that underpinned the visitor’s hefty 339 – stands of 46, 44, 94 and 39 all delivered in quick time.
Wickets came in decade intervals, and when they did it often required either magic, or batter error.
In the former category, Came was sensationally caught at midwicket by Nick Gubbins and Matt Montgomery had his off-stump glanced by an Abbott pearler,
Jewell looked on course for a second century in the competition as he strode through 400 runs in the One-Day Cup.
But having been fluently batting at a strike-rate around 120, he slowed up with the milestone in sight, and on 98 he missed a paddle sweep and was bowled by Felix Organ.
Brooke Guest and Martin Andersson regained the sweet-striking momentum, the latter with an excellent eighth List A fifty but for the eighth time he couldn’t convert.
Any chance of Derbyshire flittering at the end of their innings was kyboshed by Amrit Singh Basra – with 90 runs coming off the last 10 overs. The SACA graduate who signed a two-year contract this week showed off his range of shots in a breathless 15-ball 34 – but it wasn’t to be enough.
