Enrique Iglesias, 48, left his announcement to the final hour as he was set to perform at the famous Tecate Emblema Festival in Mexico City this weekend, headlining the first night of what was set to be a sensational celebration of music.
He sincerely apologised to his millions of fans on social media, as he explained his absence in a short statement, originally written in Spanish.
The musician shared: "Dear fans, much to my regret, it'll be impossible for me to appear at the show tonight in México.
"I have pneumonia and doctors have advised absolute rest and have forbidden me to get on an airplane.
"I am frankly sad to cancel this show in a country that has given me so much.
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"I hope to recover fast and be able to be with you all in full form soon."
While many of Enrique's 13 million Twitter followers reached out to the singer in the comments offering support, advice and home remedies, others were not so kind.
One raged: "If you already knew why didn't you warn us before? You didn't get sick today, that's not how the illness works" while others demanded refunds and shared their outrage as "I bought my ticket just to see you".
Enrique's untimely illness sent festival organisers scrambling for replacements to fill up his empty headline space on Saturday night.
The last minute fill-ins included the likes of Danna Paola, Kabah, Magneto and The Sacados among a few others.
The official Tecate Emblema organisers OCESA also released a statement following Enrique's confirmation that he wouldn't be able to attend which noted that fans who had purchased individual tickets for Saturday would also be allowed entry to the festival on Sunday or receive a refund.
Fans were still able to get their fill of music on Saturday with the rest of the sensational lineup unchanged with The Chainsmokers, One Republic and Melanie C's sets all going according to plan.
The second day of the festival will see Robbie Williams and KYGO headlining the stages with the likes of Black Eyed Peas, Becky G and Emilia filling out the lineup.