A closing round of 70 saw the Irish international triumph by five shots from Kent champion Liam Burns, who signed off with 73.
As soon as he signed his card and had added to his compatriot Sean Lowry's triumph in the Irish Open, Kearney said: “It’s great. I heard about it when we were coming up the 14th. That news spurred me on to complete my victory.”
Kearney becomes the first Irishman since Ronan Rafferty at Hunstanton in 1980 to win the Brabazon Trophy, but the latter had to share the title with Peter McEvoy on that occasion.
On the first he holed his bunker shot for an three before adding another eagle at the seventh in an outward 33 which put an end to Burns' challenge.
In third place was 20-year-old Joe Vickery, while England's Dale Whitnell climbed the leaderboard with a 69 to share fourth place on 216.
The battle for the Henriquez Salver for the best performance by a Great Britain and Ireland player aged under 20 proved a four-way tie between Tommy Fleetwood, Matt Nixon, Stiggy Hodgson and Ireland’s Alan Dunbar who all finished on 216.
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