The "View" host announced her baby news on the show Monday. The former "Survivor" contestant is due in November.
"I figured that we're going to be lonely without you (Rosie) so Tim and I thought we should get busy and you know, maybe make a little cohost," she said.
Hasselbeck and her husband, NFL Quarterback Tim Hasselbeck, will celebrate their five-year anniversary in July. They have a 2-year-old daughter named Grace.
"Tim and I are incredibly thankful and excited," Hasselbeck said in a statement released by the network on Monday.
Hasselbeck's co-host, Rosie O'Donnell, announced last week that she's leaving the show (currently celebrating its 10th season) in June.
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"When you said you had an announcement my heart sank," Walters said Monday, referring to the recent loss of O'Donnell.
O'Donnell said she found out that Hasselbeck was pregnant two weeks ago and it's been hard keeping the secret.