The Richmond midfielder polled 107 votes to win by eight from Collingwood midfielder Dayne Beams, with Gold Coast captain and 2007-09 winner Gary Ablett and Adelaide midfielder Patrick Dangerfield seven votes further back in third.
Cotchin entered the final home and away round knowing he had won at least a share of the AFLCA award, with Beams able to catch him only if he polled the maximum 10 votes in Collingwood's clash with Essendon and Cotchin failed to poll in Richmond's clash with Port Adelaide.
The prize was Cotchin's when Beams starred against the Bombers with 33 possessions but, with Travis Cloke and Dane Swan dominant, could manage only six votes.
Cotchin then stretched his winning margin when, after a relatively quiet first half under the close attention of Power captain Domenic Cassisi, he powered home to finish with 31 possessions and four AFLCA votes.
It was the 20th match this season in which Cotchin had polled AFLCA votes, with his only voteless games coming in rounds three and six.
The 22-year-old has emerged as one of the competition's best midfielders in 2012, averaging 27.5 possessions a game.
He will enter this month's Brownlow Medal count as one of the favourites and, with Chris Newman stepping down as Tigers skipper last Sunday, is also widely tipped to become the next Richmond captain.
Round 23 votes
9 Brad Ebert (Port)?
8 Jack Riewoldt (Rich)
4 Trent Cotchin (Rich)?
4 Bachar Houli (Rich)?
3 Jay Schulz (Port)?
2 Kane Cornes (Port)
FINAL LEADERBOARD
107 Trent Cotchin (Rich)?
99 Dayne Beams (Coll)?
92 Gary Ablett (GC)?
92 Patrick Dangerfield (Adel)?
90 Scott Thompson (Adel)?
89 Jobe Watson (Ess)?
84 Matthew Boyd (WB)?
79 Josh Kennedy (Syd)?
76 Scott Pendlebury (Coll)
73 Brett Deledio (Rich)
