Murray Goodwin stroked a measured unbeaten 79 as Sussex swapped bottom place in the Twenty20 Cup south division with opponents Surrey.
Goodwin's classy 46-ball knock guided Sussex past Surrey's 164-8 with 16 balls to spare in a six-wicket win.
Sussex's victory maintains their hopes of reaching the quarter-finals, but Surrey's are now officially at an end.
Ali Brown blasted 51 from 21 balls, but the visitors slumped from an excellent 102-2 after 10 overs of their innings.
Opener Goodwin fired nine fours and two sixes, and he shared in a superb third-wicket stand of 117 in a dozen overs with Matt Prior (56).
It came at a good time after the Sharks, with five defeats in their previous six games, made an uncertain start with Jade Dernbach (3-23) removing Chris Nash (0) and skipper Chris Adams (six) in the first two overs.
Goodwin and Prior batted in enterprising fashion before a crowd of 6,200.
And Sussex only required a further nine when Prior, after compiling eight fours and a six off 37 balls, holed out at long-on off Dernbach.
Surrey had seemed poised for a good total after Mark Ramprakash had won the toss.
He put on 84 with Brown, but three run-outs unhinged the Surrey innings and left them well short of a good total.