The gig was scheduled to take place at the Bell Centre on Monday evening, reported Entertainment Weekly.
"To my beautiful fans. I couldn't be more devastated that I am unable to perform tonight. I sing this entire show live, and pride myself in giving it all, but when I sang in the rain at Citi Field I got sick and have been pushing through.
"I am so sorry to anyone who had their heart set on seeing me tonight. I love you," she tweeted, signing the note as Joanne.