The singer, 34, and 37-year-old producer Andrew are said to have tied the knot at Hampton Court Palace in West London.
READ: KERRY KATONA ASKS WEDDING GUESTS FOR MONEY - "I'VE GOT FIVE KIDS TO FEED"
Seemingly confirming the reports of her big day, Katherine tweeted: "Thank you all for your love & support. It's already been such a special day & I wanted to share my happiness with you xxx"
An insider told the Mail last week: "Katherine and Andrew are tying the know on Saturday at Hampton Court Palace.
"They've been coy about the details surrounding the wedding and were keen to keep it under wraps.
"The couple have family flying in from America, and everyone is excited to be a part of their big day."
Katherine confirmed the news of her engagement to Andrew in April. At the time, a source said: "Katherine has been preparing the announcement for a while. She is very excited – she loves how artistic and intelligent Andrew is. He is considering moving to the UK for her."
The couple have been together since the end of last year. Katherine was previously engaged to presenter Gethin Jones, but they called it off in 2012.