People.com said Friday the 27-year-old actress, who plays Robin Scherbatsky on the CBS comedy, gave birth to daughter Shaelyn Cado Killam on May 16.
Smulders and her fiance, actor Taran Killam, announced the actress was pregnant with the couple's first child in November.
Smulders said during a January event the fact her "Mother" co-star Alyson Hannigan was also pregnant meant babies became a significant part of their conversations.
"You really can't help it, because you have babies on the brain, and you can't help but talk about it a lot," she told People magazine at the time. "From creams, doctors, birth methods, dilation ... you talk about everything."
"It's nice because we can just talk about babies all day long, and not be like, 'OK, this person has to be sick of this,' because you know that she's just as excited as I am," Hannigan offered regarding those discussions.