Willetton adapted to the tough wet-weather conditions quickly, with captain Josh Coleman kicking the first goal in the opening minutes.
The lead was 13 points at half-time in the low-scoring match.
Scarborough were unable to convert a number of chances in the third quarter and Willetton kept extending their lead through accurate goal-kicking.
Brandon Ellis ended the match with four goals and Josh Kyle kicked three in a best-on-ground performance.
The final score was Willetton 8.5 (53) to Scarborough 3.11 (29).
David Myors won his first premiership as coach and built on the successful history of the Willetton colts.