The actress, 44, and her fiancé Nicky Marmet welcomed their first child, a baby boy, on Thursday, June 23, her rep confirms to PEOPLE.
Son Oscar Holly Marmet weighed 9.1 lbs. and measured 21 inches long.
“Sorry I didn’t talk about being pregnant. Wanted to keep it all for myself,” The Mentalist star added, including the hashtags “#momlife,” “#bestbaby” and “#soinlove.”
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Tunney also posted a second photo taken by Lee, which depicts herself, Marmet, baby Oscar and their dog Rufus — the latter of whom is shown sniffing the new addition while the proud new parents smile widely.
“First photo of the whole family,” the actress captioned the snap, adding, “Rufus would have preferred we’d gotten another dog.”
— Jen Juneau