Bournemouth are in the market for a new goalkeeper following the dismissal of Ryan Allsop during Tuesday's defeat to Leeds and Cherries boss Eddie Howe has moved to bring in Henderson.
Highly-rated Henderson has found himself down the pecking order at West Ham this season following the arrival of Spanish keeper Adrian.
West Ham boss Sam Allardyce is a big fan of Henderson and is happy for him to go out and get some regular first-team action.
The 25-year-old impressed during two successful loan spells at Ipswich last season, keeping eight clean sheets in 24 appearances for the Portman Road outfit.
Former Portsmouth keeper Henderson is expected to go straight into the Bournemouth side to face Millwall this weekend.
Henderson will become the second West Ham player to join Bournemouth this after Jack Collison arrived on loan.