It was Mullets’ first appearance in a final since they lifted the John O’Hara Cup in 2004 but strikes from Callum Connor, Ryan Knight and Ryan Walton ensured victory for Newhaven at Gorings Mead.
In front of a crowd of 505, the Mullets nearly went ahead on 12 minutes but Max Thoms’ 30-yard strike was superbly tipped on to the post by Newhaven keeper Jake Buss.
Newhaven then went close but the unmarked Ryan Walton could only fire straight at Arundel keeper James Fernandes from Lee Robinson’s right-wing cross.
The miss did not prove costly as Newhaven went 1-0 up on 36 minutes. Connor got in behind the Arundel backline, rounded Fernandes and slotted into the empty net.
The Mullets should have gone in level at half-time but Scott Tipper blazed an effort over the bar a minute before the break.
Newhaven began the second period the better of the two sides and went two goals ahead on 63 minutes. Adam Kneller whipped in a fine free kick, which was guided home by Knight.
Walton then struck two minutes later to all but secure the trophy for his side. Brad Murray tried his luck from the edge of the area and Fernandes could only parry the ball into Walton’s path and he netted.
Arundel did manage to pull a goal back when Lewis Jenkins headed home Jordan Clark’s corner but that proved to be just a consolation.
ARUNDEL: Fernandes; Bibb, Walker, Peake, Hunter; Jenkins, Clark, Thoms, N.DaCosta; Boutwood, Tipper. Subs: A.Biggs (N.DaCosta), J.Biggs (Bibb), L.DaCosta (Hunter), Richards, Marsden.