The 'Senorita' singer added, "It breaks my heart to do this but my doctors told me I can not perform tonight or it would risk long term damage to my voice. I love you all so much and apologize from the bottom of my heart as I wish I could be there on stage tonight."
The star who has been traveling the world on his tour concluded, "I promise I will make it up to you next time I'm back in South America. Te Amo,"
Earlier, Mendes protested climate change in the middle of his Sao Paulo concert on Friday.
Shortly before announcing the concert cancellation, the 'Treat You Better' singer posted on Instagram "Sao Paulo you are unbelievable. Magical and strong!!! See you again tonight,"
His next concert is scheduled for December 3 in Rio de Janeiro.