Middlesex suffered their first defeat of the season as Kent chased down a target of 177 for an eight-wicket Clydesdale Bank 40 win at Lord's.
Sam Northeast and Martin van Jaarsveld struck contrasting half-centuries to see the visitors across the winning line from the final ball of the 30th over.
Opening batsman Northeast finished unbeaten on 63 from 91 deliveries, having added 119 for the second wicket with Van Jaarsveld, who was dismissed for a 73-ball 85 by part-time leg-spinner Dawid Malan (1-30) with 37 still required.
Darren Stevens (13no), who had earlier claimed 2-33 with the ball, joined Northeast to complete the victory.
Middlesex had struggled to 176-9 after being sent in, opener Scott Newman's 49 the top score as Kent's young seam duo Ashley Shaw (3-26) and Adam Ball (2-41) both made a positive impression.