The Versailles-based manufacturer landed a two-year deal with motorsport's governing body, bringing to an end M-Sport's tenure.
This year's Junior WRC champion will be crowned in a DS3 R3T, after Craig Breen, Elfyn Evans and Pontus Tidemand all won the WRC's feeder series in Ford Fiesta R2s.
In addition to the change of car, there will also be a change of tyre supplier, with Michelin replacing Hankook for the Junior WRC series.
The 2014 Junior WRC winner will tackle six rounds of the '15 WRC2 series in Citroen's DS3 R5 car. The machine is due to be homologated in March.
This year's Junior WRC will be contested over six European rounds of the WRC with crews counting all scores towards their end of season tally.
The crews can select their own six rallies from Rally of Portugal (April 3-6) onwards.
Confirmation of the Junior WRC series came too late to include Monte Carlo or Sweden.