After being tasked with scoring 224 to maintain their 100 per cent record, Notts' much-vaunted top order failed to deliver for the first time this season.
James Taylor top-scored for the home side with 48 and Samit Patel made 45 as Notts were bowled out for only 173 with the last seven wickets falling for just 47 in only 10 overs.
Earlier, after electing to bat first, Sussex reached 223 for nine with Matt Machan making 68, with hopes of a bigger total stunted by the performance of Harry Gurney who took five for 48 for Notts.
Three years ago 26-year old Gurney took a championship hat-trick against the same opposition at Hove. This time, the left-arm quick bowler removed both Luke Wright and Rory Hamilton-Brown in his opening burst before returning to claim three more wickets, including Machan, who had shared in a stand of 90 with Ed Joyce for the fourth wicket.
Many of the crowd of over 8,000, who had taken advantage of a generous discounted admission price, had come to hail the return of David Hussey to the Nottinghamshire ranks. The Australian, returning as the county's overseas player, took an early catch but then blotted his copybook by spilling Joyce, who made 58, when the Sussex skipper was on 20.
Machan's own 50 had come from 55 balls faced and included three fours and two maximums. Left with the lower order after Joe Gatting and Ben Brown had fallen cheaply, the 22-year old from Brighton tried to bolster the total by attempting some unorthodox deflections and ramp shots before his luck finally ran out and he was bowled.
Matthew Hobden, a 20-year old seamer from Eastbourne, began his debut in style for Sussex by bowling Michael Lumb in the fourth over.
The out-of-form Alex Hales failed again, making only seven before driving Andrew Miller to point where Rory Hamilton-Brown took the first of his four catches. Patel skied Chris Liddle, who took three for 21, to mid-off and Hussey only made 14 before the innings collapsed in dramatic fashion with 4.1 overs remaining unbowled.
Nottinghamshire remain favourites to win the group but will need to lick their wounds and recuperate after their winning streak ended at seven consecutive victories.