The batsman was crowned joint winner with Rockingham-Mandurah all-rounder Brendon Diamanti on Friday night.
The medal count for the best player in WA Premier Cricket was voted by the umpires on a 3-2-1 basis for each regular season game.
Swans captain Walters and ex-New Zealand international Diamanti are the first joint winners in five years.
It was the second time Walters had won the Olly Cooley medal, after being crowned best player in the 2006-07 season.
The pair polled 15 votes, finishing ahead of Fremantle’s English recruit Thomas Abell and Melville fast bowler Mark Turner on 14 votes.
Walters also took out the 2015-16 first-grade batting average award, scoring 827 runs at an average of 103.38, including three centuries, to complete a stellar night.
Walters and Diamanti were named in the Team of the Year along with players from nine other clubs, including Midland-Guildford’s Tim Armstong.