The Nigeria international struck within seconds of replacing Michael Owen with 20 minutes of a pulsating encounter remaining and the Dane secured the points with four minutes left to drag the Magpies out of the relegation zone and send Hull into the bottom three.
It was Newcastle's first home win since December 21 and just their second anywhere in 18 attempts in what Shearer had described as the biggest match of his career, and he celebrated accordingly on the final whistle.
But opposite number Gareth Southgate could have few complaints about the effort his players put in as they fought for their top-flight lives to the death, although their plight now looks desperate after an 11th successive away league defeat.
They had taken a third-minute lead when the unfortunate Habib Beye bundled the ball into his own net after goalkeeper Steve Harper had blocked Tuncay Sanli's close-range shot.
However, defender Steven Taylor levelled within six with a bullet header after Boro old boy Mark Viduka had hit the post on a night when both sides enjoyed spells of control in front of a passionate crowd of 51,252.