Carrasco, 32, made the revelation to a TV station while on a visit to a hospital in the Dominican Republic. He remains positive about his prognosis -- saying the condition is "under control" -- and said he'll be back with the team "at the end of July.''
Later Saturday afternoon, in a video posted on the Indians' Twitter account, Carrasco said a blood test after a spring training physical prompted some concern, and he was diagnosed with leukemia in May.
"I never thought that I would have something like this, because I play baseball, I'm like super healthy or something like that," Carrasco said in the video. "But you never know what's going on inside your body.
"When I found out, it made me even stronger, then I push myself to work through this. Then I have a lot of people behind me, helping me, especially my teammates and family."
Leukemia is a type of cancer that affects the blood and bone marrow. There are numerous forms of the disease, many of which are highly treatable.
The Indians put Carrasco on the injured list on June 5 with an unspecified diagnosed blood disorder, saying he was "stepping away from baseball activities to explore the optimal treatment and recovery options" and that they expected him to return "at some point this season."
Manager Terry Francona said the club has known the details of Carrasco's condition, but he declined to talk about Carrasco's condition beyond what was said in the video.
"There's nothing that came out that we didn't know," Francona said before Saturday's game. "Carlos is going to talk to you guys Thursday night at our workout. He's still throwing and doing all that."
Following his diagnosis, Carrasco spoke with teammate Jason Kipnis, who helped him research and understand what he was dealing with.
"He'll get through this with the help of everybody,'' Kipnis said last month. "I know the city will be very supportive of him. Every time anyone sees him they will wish him well and ask him how he's doing. I'm sure he'll still have a big smile on his face. He's always in a good mood.''
Major League Baseball, its teams and other franchises and individual players across the sports landscape took to social media to wish Carrasco well, using #CookieStrong.
Carrasco has developed into one of the AL's steadiest pitchers in recent years. He won 17 games last season and went 18-6 in 2017, when he finished fourth in the AL Cy Young Award voting.
He was 4-6 with a 4.98 ERA in 12 starts this season prior to going on the IL.
Carrasco signed a four-year, $47 million contract in December. In 10 seasons, all with the Indians, he is 83-68 in 219 appearances (183 starts).
The Associated Press contributed to this report.