Cheika backs Lealiifano to beat leukaemia
The Brumbies said over the weekend that Lealiifano had been diagnosed with the cancer that affects the blood and bone marrow following a brief illness.
Several Wallabies visited 28-year-old Lealiifano over the weekend to offer him their support.
"I certainly believe he's going to get through and get through well," Cheika told reporters at the team's training camp.
"He's a tough guy. He's shown that over many years of playing footy and in the experience that I've had with him, he's always shown that and I'm backing him 100 percent.
"He's up for it, there's no doubt about it. The lads have been in contact with him and a fair few of the boys have been to see him already, but he's right up for it."
Wallabies captain Stephen Moore said the players were in shock following the news of Lealiifano's illness.
"I think he knows we're all here to support him the whole way," Moore told reporters.
"We spoke about that as a group, just making sure we continue our support for him as he continues to go through this treatment.
"We've got to make sure we stay positive around him, right through his whole treatment. We don't know how long that's going to be, so we'll make sure we're always there for him and make sure that he knows that."
Lealiifano has played 19 Tests for Australia and 117 Super Rugby games for the Brumbies.
Agence France-Presse