Lester said his father John was diagnosed with lymphoma last month and that the cancer is "slow growing, ... something [his father] will die with, not die from."
Father and son will get to talk in person about their unfortunate common bond on Sunday. Jon Lester made his first start since the no-hitter Sunday afternoon against the Athletics, going just five innings and taking the loss 6-3.
Then the Red Sox will travel to Seattle where they open a three-game series against the Mariners on Monday night. The elder Lester lives in Puyallup, Washington.
Jon Lester said his father is doing well and has two more treatments to go. The 24-year-old pitcher said that his father is proud of him, but after learning first hand what his son had to go through, "He's more proud of me on another level."
After the no-hitter, Lester and Red Sox manager Terry Francona had an emotional embrace. Everyone understood then what the pitcher had been through to get to this point -- or at least they thought they did.
While none of Lester's teammates knew of his father's cancer, Francona had been told what was going on. That was likely why Lester had said he wanted to keep his conversation with his manager private after the game.
Father and son had debated whether or not to talk publicly about his dad's condition. John Lester wanted his son to get it off his chest.
"He's telling everyone ... like he won a prize," Jon Lester said. "It makes him feel better to sit there and talk about it. He can tell people, you know what, I have cancer, I'm doing great, everything is going to be good and people look at him like he's crazy. I guess that's how everyone looked at me when I told them."
Jon Lester learned of his father's medical problems during Boston's opening series at Fenway Park when they got their World Series rings.
Jon Lester, who was diagnosed with a rare form of non-Hodgkin's lymphoma nearly two years ago, earned the victory in the clinching game of Boston's sweep of the Colorado Rockies last year.
When his mother sat him down to deliver the news, Lester knew the seriousness of the situation.
"You hear the word cancer, and you figure death," Lester said.
When the Lesters meet up Sunday night, Jon is bringing a special gift for his dad. He'll have a brand new Red Sox World Series hat with him to cover his father's head that is now bald due to cancer treatments.
"Usually your parents get it before you do or whatever it may be if you get it," Lester said. "He definitely remembers some of the times I had and how I approached everything and he tries to do it the same way."
Lester also has been able to counsel Anthony Rizzo, a player in Boston's farm system, who was recently diagnosed with a form of cancer.
"He didn't know that you could do the things that you want to do with the disease and still live a normal life while you have it. ... I think that gave him a positive outlook," Lester said.
Lester is an inspiration for people diagnosed with cancer but he's still getting used to his new status as a role model.
"It's weird, it definitely is," Lester said. "Like I've said before, it's not my personality to take credit for anything and to do that,"
Lester said. "When people come up to me and say you're an inspiration or you've helped me get through this, it means a lot to me but they may not get the reaction they want. But like I said I'm learning how to deal with it."
Erin Andrews is a reporter for ESPN.