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
The actress will next appear on the big screen in "Are You Here" with
Fischer will also star in "Kiss Me,"