The Amsterdam giant has completed the transfer of the attacking midfielder after already agreeing to terms with Heracles over the weekend.
The Eredivisie champion was in the market for a new midfielder due to the departure of Christian Eriksen to Tottenham last week and has snapped up the 23-year-old as his replacement. Both clubs already reached an agreement over the transfer on Saturday, and Duarte has now inked a four-year deal with the Amsterdam side to finalize the move.
Duarte started his professional career with Sparta, but he left the Rotterdam side for Heracles in the summer of 2011. He had since become a key player in Almelo, scoring 12 goals in 65 Eredivisie appearances.
The midfielder was called up for Netherlands' Asian tour earlier this summer, but he has yet to make his official debut for the Oranje.