Swiss driver Deletraz will partner ex-Formula 1 racer Kubica and Chinese driver Ye Yifei, sharing WRT’s solo Oreca 07 for the new campaign.
WRT team boss Vincent Vosse said of the line-up: “Once again, we have combined talent, youth and experience to compose a line-up.
“What really strikes in our trio for the ELMS is that it is composed of drivers that we really wanted to work with since some time and that have in common a tremendous commitment and motivation for what they do.
“I am convinced we have one of the top line-ups and can’t wait to be in Barcelona for the pre-season tests.”
Deletraz will embark on his first full season in sportscar racing after contesting the Le Mans 24 Hours for the Rebellion Racing LMP1 team last year and three rounds of the GT World Challenge Europe season with Porsche squad GPX Racing.
The 23-year-old has also been linked to the final vacant seat on the 2021 Formula 2 grid with MP Motorsport. There are no clashes between the F2 and ELMS calendars.
”I’m really glad to join Team WRT for the 2021 ELMS season,” said Deletraz. “We have a very strong line-up with Robert and Yifei, and I am sure we are going to be competitive straight away as a team.
“After my extended single-seater and LMP1 experiences, this is going to be a new challenge that I’m really looking forward to.
“There is no doubt that Team WRT is one of the most successful squads out there. I want to thank Vincent and his people for the trust and for giving me this opportunity.”
Yifei meanwhile joins WRT off the back of his Asian Le Mans Series title success for G-Drive Racing alongside Ferdinand Habsburg and Rene Binder.
Last week, WRT revealed its full driver line-up for its other LMP2 programme in the FIA World Endurance Championship, with Habsburg and Charles Milesi joining Robin Frijns.