The actress, who plays receptionist Pam Beesly in the series The Office, gave birth to her first child, a boy named Weston.
The boy was born on September 24.
“Mom and baby are doing great,” Jenna’s rep says.
Fischer married television writer Lee Kirk in July 2010, after getting engaged the previous year during a vacation in Europe.
Jenna revealed her pregnancy in May and talked about her desire to become a mom after her sister gave birth.
“I already wanted kids, but even more so now,” she said.