Rockliff (138 votes) won a close count from midfield livewire Dayne Zorko (134) and reigning two-time winner Joel Patfull (121).
The accolade was the highlight of a huge night for the 24-year-old at the Brisbane Convention and Exhibition Centre, as he also won Player’s Player Award, Members Player of the Year and the Shaun Hart Most Competitive Player Award.
Rockliff averaged 32.7 disposals and 9.1 tackles a game (both first in the AFL) and was named in the 40-man All Australian squad earlier this week.
He is just the sixth player in Lions’ merged history to win multiple Merrett-Murray Medals, joining Michael Voss, Simon Black, Jason Akermanis, Jonathan Brown and Patfull.
Zorko had the best of his three seasons to push Rockliff right to the wire.
Zorko played 21 games to Rockliff's 18, but both men missed the final round against Geelong.
The small forward averaged 22 disposals a game, including career highs of 36 and 38 in his final two matches against Collingwood and Fremantle.
NAB Rising Star winner Lewis Taylor topped off a winning week taking out the highly contested Rookie of the Year Award, while second-year forward Michael Close was the recipient of the Most Professional Award.