The 24-year-old, who this week shocked rugby league circles by defecting to Tonga from New Zealand for the upcoming World Cup, became the first forward to run for 5000m in a season in 2017.
"Jason has again had a huge year," Cowboys general manager of football Peter Parr said.
"With a season-ending injury to our co-captain Matt Scott, Jason stepped up enormously, leading by example week-in, week-out."
Taumalolo was also joint winner of the players' player award, alongside emerging halfback Michael Morgan.
