The 'Who You Are' singer, 27, delivered the sad news to her fans in a statement on Friday night (26 June).
She said: "After having an operation earlier this week, I am unfortunately suffering a longer recovery time than expected due to some problems that have occurred post the operation.
"I have been medically advised to cancel my shows this weekend. I am simply in no way to perform."
She added: "I am really sorry to all my fans in Denmark, Bristol and Belgium and I look forward to seeing you all in the future. I am truly disappointed."
Although Jessie has not shared the reason for the operation, she has been on social media to share pictures of her hospital stay.
Earlier this week, she told fans she was about to have the op but said she would not be revealing what it's for.
Jessie suffers from a heart condition, but insists the hospital stay is not to do with her heart or her voice.
She also posted a photo of her arm, with morphine drip attached.
Alongside the snap, she replied to fans asking if she is recovering well, saying: "I am not ok... I am in a lot of pain. But I'm working on it with the doctors.
"We all have our moments and one of mine is now.
"Being human sucks when you are non stop and your body says NOPE not right now."
We hope you feel better really soon Jessie!
Watch the official video to Jessie J's single 'Masterpiece' below:
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