The Toyota GAZOO World Rally Team will expand to three cars from Rally Portugal in May.
Finland's Esapekka Lappi will join countrymen Jari-Matti Latvala and Juho Hanninen in competing in Toyota Yaris World Rally Cars in the eight remaining rounds of the championship.
"Esapekka is a very young and very hungry driver, this is for sure, but of course he has not had so much time to test the car before his first rally," said team boss Tommi Makinen.
"I know that he will do his best, and the objective for him personally is the same as the objective for the whole team: he needs to finish the rallies and collect as much information as possible."
The next round is in Argentina.