In a back-and-forth first half, Nedlands made the most of their opportunities, running in three tries to two to take a 24-10 lead at the break.
In a thrilling second half, Neddies � led by a man of the match performance from No.8 Richard Naylor � were able to hold off the fast-finishing Boars.
Nedlands opened the scoring with a Kauri Cudd penalty goal, before the Neddies winger then crossed for the first try of the contest and converted to hand his side an early 10-0 lead.
Soon after, Naylor barged over to extend the advantage to 17 points.
Sensing the pressure, Wests Scarborough responded immediately, when Jordan Luke touched down in the corner before Jarome Leonard-TeKanawa dived on a grubbered ball to bring the Boars to within seven points.
Nedlands had the final say of the first half when Michael Egan stormed over for his side�s third, with Cudd�s conversion giving the minor premiers a 24-10 half-time lead.
An A.J. Alatimu penalty opened the scoring for Wests in the second half, before Nedlands fullback Dylan Loversidge responded when he stepped inside to score Nedlands� fourth of the afternoon for a 31-13 advantage.
Wests kept themselves in the hunt thanks to a converted try to Keith Andrews off the back of a rolling maul, before Cudd steadied the ship with his second penalty to push the lead out to 34-20.
Wests Scarborough�s Marty Campbell set up a potential grandstand finish when he intercepted a pass to score under the posts.
But in a whirlwind passage of play Nedlands answered, as Loversidge combined with scrumhalf Michael Ruru, who dived over from just a metre out to finalise the 39-27 result.
The Premier Grade Premiership completes a historic treble for the club, with Nedlands claiming the Under-19 and Reserve Grade premierships earlier in the day.
Nedlands 39 (Michael Ruru, Kauri Cudd, Richard Naylor, Michael Egan, Dylan Loversidge tries; Kauri Cudd 4 conversion, 2 penalties) def Wests Scarborough 27 (Jordan Luke, Jarome Leonard-TeKanawa, Keith Andrews, Marty Campbell tries; AJ Alatimu conversion, penalty, Marty Campbell conversion).
Etixx Player of the Match: Richard Naylor