The singer was taken to hospital straight after Sunday's 8am service at the Hills campus site in Sydney.
She then underwent nine hours of brain surgery and Hillsong church are asking people to pray for her recovery.
An aneurysm is a bulge in a blood vessel and it can cause sudden agonising headaches, a stiff neck, sickness and pain when looking at light.
Chelsea Taylor had a ruptured anuerysm but is now thought to be out of ICU.
In an Instagram post, Brooke Ligertwood, who wrote 'What a Beautiful Name It Is' posted: "Please pray for Chelsea, one of our beloved Sydney team. This is her leading worship at church on Sunday - she was rushed to hospital shortly afterwards, has since come through a major surgery and needs our prayer. This girl is very dear to our hearts."
Hillsong Creative posted on Sunday: "She's a worshipper, a lover of Jesus and one of the purest hearts ever - and tonight she could do with your prayers. She has just come through a 9 hour brain surgery and we are believing for no more bleeds complete healing and miracles in Jesus name - we are not out of the woods by any means - tonight she is in ICU but we believe in Jesus, his resurrection power and for hope to appear (@zellataylor and all your family we are on your team). #iloveus #ourpeople #praylikeshesyourstoo"
Hillsong worship leader Matty Crocker, who wrote the song Oceans, posted: "I am actually speechless right now... @Chelsealeetaylor we were leading worship together yesterday morning and then we both walked off separate sides of the stage. Halfway through the message I got a text saying you wouldn't be up there with us when we go back up. I thought you had fainted and that was it. I only found out in the last few hours how serious it was...
"If you read this at all, know that the Crocker's are praying with and for you. Complete healing, complete peace, complete rest... that you would know and sense His presence like never before... "Be still, and know that I am God"...psalm 46:10"
Chelsea Taylor's mum was quoted in an Instagram post from Ben Lounsbury, another Christian musician, as saying: "Chelsea pulled the life-support out last night. She is talking and trying to get out of bed
Honestly this is a miracle! The comment was said to me, the doctors aren't saying anything! Praise our faithful God".
"I just told her the whole church is praying and fasting all over the world and she smiled and said thanks mum."
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