The HELLO! Online blogger and former Coronation Street actress has had a close relationship with the hospital since 2013 when she fronted their Big T-Break campaign.
Michelle, who is also from Manchester, said: "I am really excited and honoured to become an official patron for Royal Manchester Children's Hospital Charity.
"Being born and bred in this city, I know the excellent work the hospital does and couldn't think of a better local charity to support than RMCH Charity."
She continued: "Having visited the hospital myself, I have seen first-hand the difference that the Charity makes to the patients."
"I really enjoyed visiting the hospital again and meeting the inspirational staff and patients", Michelle added.
"Now that I am an official patron I will be encouraging the people of the North-West to join me in supporting the Charity to help ensure that Royal Manchester Children’s Hospital is not only the biggest in the UK, but also one of the very best!"
Michelle has found herself back in Manchester this October to film her new BBC series, Ordinary Lies, after recently moving to Essex to live full-time with her fiancé Mark Wright.
On Thursday the pint-sized actress was pictured laden with bags as she browsed the shop windows of Manchester city centre, filming scenes for the TV drama. The star announced last month that she would be joining the BBC show, which is set in a car salesroom in the north of England.
Michelle has previously revealed on her HELLO! Online blog how eager she was to take on her new role.
"So this week I start my new job! So excited! Finally, finally I can tell you!" she wrote. "I have been cast in a brand new BBC drama series – Ordinary Lies. It's set in the offices of a motor showroom, and is about the little white lies that people tell and how they can spiral out of control."