The mezzo-soprano singer showed off the sparkler when she stepped out for the first time since the happy revelation, going for daytime casual in fitted jeans, a white blouse and a baby pink jacket. Her loose brunette locks and a pair of beige heels finished the chic look.
Katherine and Andrew at Buckingham Palace
Speaking on her mobile phone at the time, she gave the world a clear glimpse of the dazzler, which features a large oval stone surrounded by 54 small diamonds.
Katherine, 33, accepted her boyfriend’s proposal last Tuesday following a whirlwind six-month romance.
The stylish Welsh opera singer said she was "thrilled" and "surprised" by the proposal.
Katherine and Andrew have kept their relationship out of the spotlight and the singer was only confirmed as Katherine's boyfriend in March when she was awarded her OBE from Prince Charles.
The couple during a date in Soho, London
Andrew was firmly by her side as she stepped out at Buckingham Palace to receive the prestigious accolade from the first-in-line to the throne.
In pictures: Katherine Jenkins' best style moments
Katherine's friends have said Andrew proposed on 17 April, but the couple waited until all their family members had been told before breaking the news officially.
Andrew works as a professor at New York University, where he graduated in 2000, and is also an accomplished sculptor, artist and filmmaker.