The couple already have one daughter, Maxima, who was born in December 2015. They announced that Chan is pregnant with another girl on Thursday 9 March.
The 32-year-old billionaire took to his social media platform of choice (Facebook naturally) to share the good news, saying: “Priscilla and I are happy to share we’re expecting another baby girl!”
The pair have been together since 2003, after meeting at a Harvard college party, and they married in May 2012.
They had a “difficult experience” with conceiving, and went through several miscarriages.
Zuckerberg said: “After our difficult experience having Max, we weren’t sure what to expect or whether we’d be able to have another child.”
Following on from International Women’s Day on Wednesday, Zuckerberg, who grew up with three sisters, explained how pleased he was that he would be welcoming another female to his family.
He said: “When Priscilla and I first found out she was pregnant again, our first hope was that the child would be healthy. My next hope was that it would be a girl. I cannot think of a greater gift than having a sister and I’m so happy Max and our new child will have each other.”
Speaking about his own sisters, Zuckerberg added: “They taught me to learn from smart, strong, women. They weren’t just my sisters but some of my best friends.”
“We are all better people because of the strong women in our lives – sisters, mothers and friends. We can’t wait to welcome our new little one and do our best to raise another strong woman.”