In a statement posted Cain's Twitter account, a spokesperson said Cain "is resting comfortably at an Atlanta-area hospital," adding that Cain did not require a respirator and is "awake and alert."
Cain, a Black Voices for Trump co-chair, was among the campaign surrogates who attended President Donald Trump's June 20 rally in Tulsa, Oklahoma. Cain posted a photo of himself and others at the rally not wearing masks.
"There is no way of knowing for sure how or where Mr. Cain contracted the coronavirus, but we do know he is a fighter who has beaten Stage 4 cancer," the statement continued.
Trump campaign communications director Tim Murtaugh told ABC News that Cain did not "meet with" Trump in Tulsa.
"Contact tracing was conducted after the Tulsa rally but we do not comment regarding the medical information of individuals," Murtaugh added.
ABC News contributed to this report.