Credit: Frazer Harrison/FilmMagic

Mad for Xander!

Less than a month after giving birth, new mom January Jones got back to work on the Los Angeles set of Mad Men on Tuesday.

Another first? For the first time, stepping out of an office building nearby, the 33-year-old star gave the world a good glimpse of her baby son Xander Dane Jones, born Sept. 13.

Wearing shades and a lacy top, the actress held her little boy (adorable in patterned PJs and clutching his mom) close. See more pics of January and Xander from PopSugar.

Jones hasn't yet identified Xander's dad.

"He's beautiful," her Mad Men costar John Slattery told Us a few weeks ago. "She's in love with that boy."

At the Emmys, Mad Men costume designer Janie Bryant added that Jones seemed "wonderfully happy" in her first days as mom. "She is a loving, wonderful, hilarious girl who is an amazing wit and character. I think she's one of the best!"