D.J. Campbell's two second-half goals gave Blackpool a 2-0 win on Tuesday to end Sunderland's undefeated home record in the Premier League this season.
It was Blackpool's fifth away league victory since being promoted this season, having won only twice at home by comparison.
Campbell, who had previously played under Sunderland coach Steve Bruce at Birmingham, struck a volley in the 52nd minute in front of 42,892 fans at the Stadium of Light to punish the hosts for missing numerous chances.
The forward added a second goal from substitute Matt Phillips' cross in the final seconds to seal the victory.
Blackpool is eighth in the standings with 25 points, two behind seventh-place Sunderland.
It was Blackpool's first game for 17 days after its past three home matches were postponed due to the cold weather that has swept through Britain over the past month, and the team was missing captain Charlie Adam.
Sunderland welcomed back captain Lee Cattermole from suspension and Danny Welbeck, the on-loan striker who was ineligible to play in the 2-0 loss to Manchester United on Sunday.
However, the hosts squandered six good chances in the first half despite boasting an attack that included Welbeck, Darren Bent and Asamoah Gyan.
Bent shot across the face of goal after 11 and 32 minutes, and Gyan, who had earlier driven the ball into the side-netting from a tight angle, wastefully scuffed wide from Ahmed Elmohamady's injury-time cross with the goal at his mercy.
Blackpool gradually worked its way into the game and had chances of its own. The best of them fell to Campbell.
Phillips eluded Welbeck and defender Phil Bardsley and crossed for Campbell, who failed to hit the target despite being in space.
Campbell went closer in the 38th, firing a low 20-yard drive just wide with goalkeeper Craig Gordon scrambling to get across to cover the shot.
Sunderland started the second half dominantly, but it was Blackpool which took the lead after the hosts were caught out at a corner.
Neil Eardley collected David Vaughan's short pass and crossed for Ian Evatt to flick on the ball, allowing Campbell to volley home from close range.
Sunderland responded but Gyan could not keep his 58th-minute shot down as he slid in to meet a cross at the near post.
Sunderland attacked relentlessly as fulltime drew closer, forcing goalkeeper Richard Kingson into making a series of saves, denying substitute Steed Malbranque in the 80th and then blocking Bent's attempt four minutes later.
Bent hit the crossbar with a free kick in the 86th minute, and Blackpool made the game safe with time almost up.
