The Eagles decided to name the award after Worsfold for his outstanding contribution to the club over 24 of West Coast's 27 years of existence, following his resignation as senior coach after 12 years and 281 matches at the helm.
Worsfold, a two-time premiership captain and 2006 premiership coach with the Eagles, won the award as a 20-year-old in 1988.
Priddis claimed the inaugural John Worsfold Medal on Friday night at Crown Perth's Grand Ballroom after twice finishing runner-up, in 2010 and 2011.
The 28-year-old midfielder was rewarded for a superb season, topping the voting ahead of Eric Mackenzie and Josh Kennedy, who were both named in this year's All Australian 40-man squad. Dean Cox and Jack Darling rounded out the top five.
Priddis (373 votes) won by six votes from Mackenzie under a voting system where each player is given a rating of one to five per game from five members of the match committee, meaning that a player could poll a maximum of 25 votes per round.
Priddis averaged nearly 27 disposals across 21 matches this season. He led the Eagles for contested possessions (298) and was second for tackles laid (129).
It was a big night for the hard-working midfielder, who was initially drafted as a mature-age rookie in 2006, as he was formally inducted as a life member of the club following his 150th match against Collingwood in round 22.
Life memberships were also awarded to long serving club stalwarts Chris Summers, Peter Souris and Ken Godwin.
Recently-retired premiership player and newly-appointed development coach Adam Selwood received the Chris Mainwaring Medal as best clubman, while second-year ruckman Scott Lycett was named rookie of the year.
John Worsfold Medal - Top 10
1. Matt Priddis - 373 votes
2. Eric Mackenzie - 367
3. Josh Kennedy - 363
4. Dean Cox - 348
5. Jack Darling - 330
6. Darren Glass - 326
7. Scott Selwood - 319
8. Andrew Gaff - 284
9. Chris Masten - 278
10. Josh Hill - 271