McEachran last featured for Chelsea in January 2012 and has since had loan spells at Swansea City, Middlesbrough, Watford and Wigan Athletic.
The 21-year-old has been hailed as the brightest English talent to emerge from the Blues' academy in a decade but has failed to establish himself in the first-team squad at Stamford Bridge.
McEachran, an England Under-21 international, is the third Chelsea player to be loaned to Vitesse this summer after Brazilian defender Wallace and Bertrand Traore.
"Josh is a talented player who can play as a controlling midfielder," said the Dutch club's technical director Mo Allach.
"I have seen Josh several times last season so his qualities are well-known to us and we are convinced that he can show them here."