Steve Bruce's men travelled to his former club having not won since early October and scored just twice in their last nine outings.
The misery looked set to continue when Adam Johnson, who scored a last-gasp winner as Sunderland beat Newcastle United last time out, capitalised on a defensive error to give the hosts the lead after just 29 seconds.
However, Gaston Ramirez equalised in the 32nd minute with his maiden goal for Hull - the Yorkshire club's first in the league since December 3 - and James Chester headed home shortly after half-time.
Substitute Nikica Jelavic then added a third in stoppage time to wrap up a valuable win and lift Hull up to 17th.
The triumph - Hull's fourth in a row against Sunderland - also eases the pressure on Northumberland-born Bruce, who occupied the Stadium of Light hotseat between 2009 and 2011.
Current Sunderland head coach Gus Poyet, without the injured Anthony Reveillere and suspended Connor Wickham, handed rare starts to Billy Jones and Ricky Alvarez.
Bruce made several changes, with Stephen Quinn, Liam Rosenior and Sone Aluko coming in, and the Hull manager was boosted by captain Curtis Davies passing a late fitness test.
Within a minute, however, Davies' head was in his hands. The centre-back's under-hit backpass allowed Johnson to race into the Hull box and clip the ball home.
John O'Shea headed a 10th-minute corner narrowly over, before Jordi Gomez and Johnson combined delightfully to present Sebastian Larsson with a glaring opportunity, only for the latter to scuff the ball wide.
Hull found their rhythm thereafter, with Ramirez producing some nice touches, and they got their reward just past the half-hour.
There appeared little danger when Ramirez received possession with his back to goal, 25 yards out. However, the Uruguay international effortlessly spun away from O’Shea and his low shot from the edge of the box, aided by an awkward bounce, went over the outstretched arm of Costel Pantilimon and into the bottom corner.
The remainder of the half was all Sunderland. Alex Bruce appeared to handle the ball inside the Hull box, but the hosts' vociferous appeals for a penalty were rejected, while Davies hacked the ball off his own line and McGregor denied Alvarez and Santiago Vergini.
Hull went ahead six minutes after the restart, with Chester slipping his marker and heading home Ramirez’s corner at the near post.
Thereafter, the visitors began to control the game, with Steven Fletcher heading Davies' header off his own line.
Sunderland began to push forward as the game wore on, but were limited to hopeful balls into their opponents' penalty area as Hull defended resolutely.
And with virtually the last kick of the game, with Sunderland committing men forward, Jelavic was left in space on the counter-attack and stuck the ball neatly into the bottom corner.
