The 19-year-old won the Addicks’ player of the season vote last season after a stunning first campaign in the centre of The Valley midfield.
Son of Gus, Diego was linked with a move to Sunderland after turning down the latest contract offer from Charlton but now looks set to make the short trip across the River Thames to Upton Park.
Sam Allardyce has been told by the club’s owners to play a different style of football and Poyet certainly fits the bill with his grace in midfield.
Ipswich Town’s Aaron Cresswell is also set to join the East Enders, with Allardyce poaching the best Championship players to bolster his mid-table Hammers outfit.
Poyet was born in Spain, with a Uruguayan father, however has played for England at youth level and has been tipped to break into the under-21 side this season should he find first team football.