The Burkina Faso international, who only joined the Blues on New Year's Day, becomes the seventh player to move from Stamford Bridge to the GelreDome this season
Traore, who only signed a four-year deal with the Blues on New Year's Day, becomes the seventh player to move from Stamford Bridge to the GelreDome this season.
The 18-year-old impressed in three matches on the Blues' pre-season tour of Asia and has been regarded as one of Africa's top young talents since making his senior international debut for Burkina Faso at 15.
On announcing the deal, Vitesse technical director Mohammed Allach said: "Bertrand Traore is generally seen as a top talent. He is a player who wants to attack and we are very excited about that.
"We know everything about his abilities, because last season he was with us on a trial. We expect him to continue his development in Arnhem during the next six months."
Traore will join fellow Chelsea loanees Lucas Piazon, Christian Atsu, Patrick van Aanholt and Cristian Cuevas at Vitesse, while Gael Kakuta and Sam Hutchinson return to west London.
Vitesse currently lie second in the Eredivisie and are level on points with leaders Ajax, though their reliance on the Blues' loan contingent has caused controversy in the Netherlands.