The actress also reflected on the experiences that had brought the family to the birth of their younger daughter, whom she has nicknamed Philo.
“We are so grateful for the crazy wild up and down journey that brought us to our little Philo!
“Family officially complete. Time to bring Matilda’s baby home! @tommypelphrey life exploded the minute we met, and the gifts keep coming. I love you forever, girl daddy!”
The announcement was accompanied by photographs of the newborn in hospital, as well as additional images and videos posted to Cuoco’s Instagram Stories.
One photograph showed Philomena wrapped in a blanket, with Cuoco writing: “She’s here!”
Another image featured Matilda smiling in a T-shirt bearing the words, “Big Sister”.
Cuoco captioned the photograph: “Someone waiting at home for us!”
The birth comes after the actress documented parts of her second pregnancy on social media, sharing photographs of her growing baby bump and family preparations.
When she first announced that she was expecting another child, Cuoco posted pictures of herself, Pelphrey and Matilda standing beside a cake covered in rainbow sprinkles.
The cake carried the words, “It’s a … ”, with a missing slice revealing a pink interior to announce that the couple were expecting another girl.
Cuoco also included a photograph from a medical appointment showing a sonogram.
Announcing the pregnancy, she wrote: “Completing our little family, what a dream come true!”
She continued: “This second time around journey has been a little windier in many ways, but wow, we are so grateful for this moment!! Little sissy on the way!!!”
Cuoco also joked about one of the ultrasound photographs, writing: “@tommypelphrey girl dad for life, and yes, the last pic is our dainty princess giving us the middle finger!”
The actress subsequently celebrated the pregnancy with a fiesta-themed baby shower attended by friends from the entertainment industry.
Guests included Lacey Chabert, 44, Kimberly J. Brown, 41, Amy Davidson, 47, and Ashley Jones, 50.
Cuoco shared photographs from the gathering, including an image of herself holding Matilda while the pair wore co-ordinating dresses.
She wrote on Instagram Stories: “Today was just the sweetest.”
The new arrival follows a successful period for Pelphrey, whose television career includes acclaimed performances in Ozark, Banshee and Outer Range.
In September, while attending the 2026 Emmy Awards, where he won Outstanding Supporting Actor in a Drama Series, the actor spoke about preparing for fatherhood again.
Speaking to E! News, Tom described the family’s excitement about welcoming another child, while acknowledging the transition from one daughter to two would bring changes.
“We’re both so excited. Our daughter’s excited. We’ll see how it goes when it actually gets there.”
The actor explained he and Cuoco had been reorganising their home to accommodate the new baby.
He said they were “switching rooms, swapping things around, and laughing at how different it is from one to two”.
“The things that are new and the things that feel like not a big deal this time. But mom and baby are healthy, so God willing, that keeps up, and we’re thrilled.”
The couple welcomed Matilda in March 2023, before announcing their engagement the following year.
The actress has previously discussed the pressure she experienced to expand her family almost immediately after becoming a mother for the first time.
Speaking to People, she said: “The minute I had my baby, they’re like, ‘When’s your second one?’ I’m like, ‘Oh my God, is anyone gonna just let me just enjoy this?’”
She also revealed in September 2024 that she and her fiance were in no hurry to arrange their wedding, despite becoming engaged the previous month.
Cuoco told People they “haven’t started planning anything yet” and suggested that “maybe another kid will have to come first”.
The actress became an international television star through her portrayal of Penny in The Big Bang Theory, appearing alongside Johnny Galecki, 51, and Jim Parsons, 53, throughout the sitcom’s 12-season run.
She subsequently received critical acclaim for playing flight attendant Cassie Bowden in HBO’s dark comedy thriller The Flight Attendant, for which she earned Emmy nominations.
Her other television credits include 8 Simple Rules, Charmed and the Peacock comedy thriller Based on a True Story, in which she starred opposite Chris Messina, 52.
Cuoco has also voiced Harley Quinn in the adult animated superhero series of the same name, expanding her career beyond live-action comedy and drama.