Alessandra Ambrosio in Brentwood, Ca on June 7, 2012. Credit: FXMX SPOT/AKM-GSI

Those Victoria's Secret models seem to bounce right back post-pregnancy!

On Thursday, just one month after giving birth to son Noah, Alessandra Ambrosio looked nearly as slim and trim as she did during her pre-pregnancy days.

Taking a stroll in the Brentwood area of Los Angeles, the 31-year-old catwalker debuted her post-baby body in a short lavender cotton frock, which she paired with flat brown leather sandals.

She and her longtime fiance, Jamie Mazur, welcomed Noah, who joins big sister Anja, 3, into the world on May 7. But true to supermodel form, Ambrosio is already back to toning up her famous, money-making body.

"First day of exercising. Feels good, but it's not easy!!" the Brazilian stunner tweeted on Friday.