Visited the maternity section of the store in London's Oxford Street with two bodyguards
The 31-year-old royal, pregnant with her first baby, currently expecting her first child with Britain's Prince William, and the spotlight is on how she will dress her growing bump.
The duchess - who is due to give birth in July - was spotted in highstreet favourite Topshop where fellow shoppers tweeted their surprise at seeing the duchess in the flagship London store.
"Oh Just an average day, Kate Middleton smiled at me! :) oh best bit... This was in Topshop! Truly Beautiful :) (sic)," Twitter user Layla Maan wrote this week, while another wrote: "So Kate Middleton was in topshop today, knew it was her, browsing alongside me! What a champ! (sic)."
According to marieclaire.co.uk, the duchess was accompanied by two royal protection officers in the store was "reportedly happy and smiley".
It isn't the first time shehas taken to the high street to shop for maternity wear.
The much-admired style icon was spotted shopping for maternity jeggings in gap, with an onlooker telling British newspaper The Telegraph: "Everyone in the store seemed to recognise her, but they gave her space and privacy to shop."
Topshop founder and billionaire Sir Philip Green recently praised the star's fashion credentials.
"I think she's done a fabulous job for England, for UK Fashion,” he gushed. "She's leading what she does, she's fabulous. She carries herself very well, it can't be an easy position, but she handles herself very well."