This will be the first time in 13-years that Yamaha has entered a factory squad in the event.
Smith and Espargaro will make their respective debuts at the race along with Japan Road Race JSB1000 champion Katsuyuki Nakasuga on a specially develop Yamaha YZF R1.
The 38th edition of the race will be held at the Suzuka circuit in Mie Prefecture on the 23-26 July.
There were rumours doing the rounds that Valentino Rossi would be competing in the event and that now clearly is not the case.
Smith says he's excited to take part in the prestigious endurance event.
"I think it will be an unforgettable event and it will add another chapter to my life with Yamaha," Smith said.
"I'm also very excited to try the new Yamaha YZF-R1, which I have heard a lot about and it will be really great to finally get the opportunity to ride it," he added.
Smith's MotoGP Tech 3 team-mate Espargaro said thatb he was aware of just how tough the event is.
"I feel honoured to take part in it, but there will be a lot to learn," Espargaro said. "I am under no illusion that it will be easy as I have never raced in an endurance event before and I don't know the YZF-R1, even though a lot of people speak very highly about it.
"The MotoGP calendar is very demanding and we will have to work through the training for the event, in between the races. Therefore, we need to work as much as possible in order to be prepared for the race, but I'm very excited to get this opportunity," he added.