Carey tweeted that Cannon, 31, is suffering from "mild kidney failure." His representative confirmed Cannon's hospitalization in Aspen, Colo., where he and Carey were vacationing.
She asked for prayers and said Cannon's situation was "very painful." She later called it a "serious moment that's very tough on all of us."
The two became parents of twins, a boy and a girl, last year.
Cannon's representative had no further information Wednesday about his condition, but said he is still hospitalized.
The Associated Press contributed to this report.