The businesswoman, who is also mum to Arabella Rose, four, and Joseph Frederick, two, shared the happy news on her Instagram account, posting an image which announced 'It's a boy! We welcome with love Theodore James, March 27 2016, 5:43pm'.
Writing alongside the picture, Ivanka told her 816,000 followers, 'Jared and I feel incredibly blessed to announce the arrival of Theodore James Kushner. Jared, Arabella, Joseph and I are so excited to welcome this sweet little boy to our family!'
Some wellwishers pointed out that both Theodore and James are the names of former American presidents, although neither Ivanka or her husband Jared Kushner, an American businessman and investor, have confirmed whether or not this was the inspiration behind the traditional moniker.
She later uploaded a second photograph to introduce the little one to the world.
Ivanka first announced that she was expecting a third child on her social media accounts in September 2015, getting Arabella and Joseph involved in an adorable photo and video shoot.
'Arabella and Joseph are both incredibly excited to have a new sibling on the way (of course, Arabella desperately wants a baby girl, and Joseph hopes it's a boy!), and I wanted them to join me in making the announcement,' she explained on her website.
'Arabella is a ham and was totally camera-ready, but I had to resort to bribery to get Joseph to cooperate. I usually try to feed my kids healthy food, but I gave Joseph his first lollipop ever in exchange for his best behavior. It's the mommy trick we all say we'll never do, but when you have multiple children, it's pretty hard to be above it - it just works too well!!
'I consider myself incredibly fortunate to have a career that I am deeply passionate about, but, at the end of the day, it's my family that is at the center of my life - and to be adding another baby to our family is a tremendous blessing. Jared and I are so thankful, and so excited!'