Subs Not Used: Krul, LuaLua, Kadar, Donaldson.
Att: 9,647
Andy Carroll headed Newcastle ahead six minutes before the break, but Brett Ormerod levelled in first-half stoppage time when he hit home from close range and Jason Euell secured the three points for the home side, smashing in a loose ball midway through the second period.
Blackpool could have gone ahead with their first real effort on goal as when Euell broke down the left and fed Ormerod, he fired in a fierce shot that Harper could only parry at full stretch.
The rebound fell to Hameur Bouazza, who had the easiest of tasks to tap in, but the linesman had already raised his flag.
Harper was soon again called into action when Ormerod turned provider and found David Vaughan, but the midfielder, in a great position eight yards out and unmarked, could not connect properly and scooped the ball into the grateful clutches of the busy Newcastle 'keeper.
The pressure continued and Harper was keeping his side in it as he made a string of fine saves, twice denying both Bouazza and Keith Southern as Blackpool searched for the vital goal their dominance warranted.
Having weathered the storm, Newcastle showed their quality and took the lead in the 39th minute with their first foray into the Blackpool area.
Joey Barton whipped in a pinpoint cross for Carroll and the striker produced a fine header at the far post to beat Paul Rachubka.
The hosts were not deterred by the setback and deservedly levelled in first-half stoppage time.
Charlie Adam unleashed a fierce drive that Harper could only fend out to Ormerod and the veteran striker breached Newcastle's defence for the first time in 545 Championship minutes by tapping in the loose ball.
Ian Holloway's men continued in the same vein in the second period and finally took the lead their endeavour deserved just after the hour mark.
The Seasiders forced a corner and after a near-post flick, a mad goalmouth scramble was ended by Euell smashing the ball home.
Newcastle inevitably upped their game in search of an equaliser and spurned three great chances to grab a point.
Kevin Nolan headed wide, Geremi fluffed his shot from a good position and Stephen Crainey cleared off the line as the hosts held out for a worthy win.