The actress, who played affable secretary-turned-saleswoman on the long-running NBC mockumentary, welcomed her baby girl in late May and somehow managed to keep the arrival a secret, according to E! News, which first reported the news.
"We are pleased to announce the birth of our daughter Harper Marie Kirk," Fischer and husband Lee Kirk told the site. "Born May 25, 2014. The family is doing great. We are happy, healthy and sleepy."
Indeed, the little one is seen getting some shut-eye in a snapshot Fischer shared with E! News.
It's the second child for the actress and the director, who wed in July 2010. The pair welcomed son Weston Lee in September 2011.
Fischer, who announced she was pregnant again back in February, was out and about during her term.
In March, she shared a bikini photo showing off her burgeoning baby bump as she posed on the beach for her 40th birthday.
In April, she joined other expectant celebrities at the launch of Jennifer Love Hewitt's new maternity line, L by Jennifer Love Hewitt, at A Pea in the Pod in Beverly Hills. Later that month, Fischer reunited with her "Office" coworkers John Krasinski, Oscar Nunez and Angela Kinsey for costar Brian Baumgartner's wedding.
The actress will next appear on the big screen in "Are You Here" with Owen Wilson, Zach Galifianakis, Amy Poehler and Melissa Rach. The comedy, directed and written by "Mad Men's" Matthew Weiner, is set to hit theaters on Aug. 22.
Fischer will also star in "Kiss Me," "Survivor" host Jeff Probst's second directorial project, and in Neil LaBute's DirecTV series of short films called "Ten X Ten," which has also tapped Adam Brody, Bill Pullman and Maggie Grace among others.
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