Northamptonshire captain Alex Wakely recorded his maiden one-day century as the Steelbacks claimed a 29-run win over Kent in the Yorkshire Bank 40.
Opener Rob Newton also chipped in with a fine 88 as the visitors reached a total of 263-4 at Tunbridge Wells, with Kent being dismissed for 234 in response.
Trent Copeland finished with 4-46 and Lee Daggett took 2-28 from his eight-over allocation as the hosts failed to keep up with the required rate on a fast-scoring ground.
It was Kent's third defeat in seven games in the competition and, even though they remain in second place in the group table, they will now struggle to qualify as Group A leaders Nottinghamshire already have five wins from five.
Wakely's 102 came from just 77 balls, with four sixes and seven fours, and he provided the major impetus with a stream of fine strokes, including three extra cover boundaries in a single over from off spinner Adam Riley.
Newton was never as fluent, as his 88 took 103 balls, but he struck two sixes and eight fours in all and was just beginning to hit his stride when he was forced to retire hurt with an ankle injury in the 35th over.
No other Northants batsman managed to reach 20 as the second-wicket stand of 144 in just 18 overs lay the foundation for a comfortable victory.
Kent began their chase well as Sam Northeast (41) added 64 for the first wicket with Sam Billings, who went on to take the score to 132-1 with Brandan Nash.
But a mid-innings collapse to 149-5, triggered when Nash (32) skied a catch and Billings was bowled swinging at Daggett for 57, left them with too much to do in the last 10 overs.
Alex Blake did his best to revive the innings by hitting 43 from just 24 balls but he was eventually dismissed by Copeland, who went on to remove the next three batsmen as well to bolster his figures.