Dragons veteran de Belin will join the Eels next season and miss the chance to become the joint venture's most-capped player.
The forward's management had opened up talks for a Dragons extension last month but AAP has been told a move to Parramatta has since been agreed upon.
The contract currently sits in the NRL's mandatory 10-day cooling off period, but barring a sudden change of heart, de Belin will join the Eels' rebuild under coach Jason Ryles.
The three-time NSW representative helps replenish a forward pack that has lost Bryce Cartwright and Joe Ofahengaue since Ryles took charge this year.
The 34-year-old made his NRL debut for the Dragons in 2011 and has played 242 games for the Red V - 31 shy of the club record set by 2010 premiership captain Ben Hornby.