'Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky,' the new mum-of-two told her 1.09 million Twitter followers.
She then posted a picture of herself and her husband with the new arrival, adding, 'At 7:41 AM Saturday, our family and hearts expanded with Aidan's arrival. We are blessed.'
https://twitter.com/ChelseaClinton/status/744628492210405376Chelsea and investment banker Marc married in July 2010 and are already parents to daughter Charlotte, who was born in September 2014.
The 36 year old wasn't the only one posting celebratory pictures of her newborn either, as her father, former president Bill Clinton, added a touching Father's Day tribute.
Aidan has made two dads very happy this Father's Day. Hillary and I are thrilled for Marc and Chelsea! pic.twitter.com/vPuwDA3Lvr— Bill Clinton (@BillClinton) June 19, 2016
'Aidan has made two dads very happy this Father's Day. Hillary and I are thrilled for Marc and Chelsea!' he wrote.
Hillary also shared a cute family snapshot of herself and Bill cradling Aidan, adding, 'What a joy being with our new grandson, Aidan. So grateful. -H'
What a joy being with our new grandson, Aidan. So grateful. -H pic.twitter.com/0687tOERez— Hillary Clinton (@HillaryClinton) June 19, 2016
In a joint interview earlier this year, Chelsea and her mother Hillary discussed the perks of motherhood and grand-motherhood respectively.
'Watching Chelsea mother Charlotte is just the greatest joy,' Hillary revealed. 'And I also occasionally feel a little bit happy that I kind of see something coming back that I maybe did or said.'
Chelsea added that she hoped to pass on to her daughter 'the same gift of imagination and kind of sense of possibility that my mom gave me.'
While still pregnant with Aidan in February, she said, 'I very much hope we'll be able to welcome her little sister or little brother as a healthy happy, giggly little person this summer.'
We're so pleased to see that he's arrived safely - congratulations, Clinton family!