Having won it four times out of the last five campaigns, Newcastle Reserves missed out on a place in the semi-final after losing 3-2 to Bedlington Terriers.
A United side featuring Shane Ferguson (pictured right), Nile Ranger, Adam Campbell, Mehdi Abeid and Romain Amalfitano took the lead when Shane Ferguson fired home direct from a free-kick.
But a crowd of 375 at Dr Pitt Welfare Park saw Bedlington equalise just before the end of an even first half.
They were awarded a free-kick on the edge of the box and Mark Convery hit a powerful right-foot effort into the roof of the net.
The hosts then took the lead early in the second half when former Magpie Mark Doninger lobbed Jak Alnwick with a superb 35-yard effort.
And Bedlington extended their lead on 71 minutes when Richard Pell scored at the back post following good work by Convery.
But United pulled one back and set up a tense finish when JJ Hooper put Ferguson in with a slide-rule pass, and the Irishman slotted home.
Newcastle pressed in the final few minutes but were unable to prevent the Ebac Northern League side from recording a memorable victory.
BEDLINGTON TERRIERS: Norton, Baxter, Cave, Carr, Pell, Wilkinson, Convery, Doninger, Bannister (Brayson), Morton (Gate), Bowey.
NEWCASTLE UNITED RESERVES: Alnwick, Logan (Riley), Ferguson, Miele, Satka, Streete, Maddison (JJ Hooper), Abeid, Ranger, Campbell, Amalfitano.
The Northumberland Senior Cup is an annual football competition held between the clubs of the Northumberland Football Association which was first played in 1884.
The current holders are Newcastle United Reserves who defeated Team Northumbria 4–2 on penalties after a 4–4 draw at St. James' Park on 30 April 2012.